Sound reinforcement system
A sound reinforcement system consists of the combination of microphones, signal processors, amplifiers and speakers that increase the intensity of pre-recorded or live sounds and that can also distribute those sounds towards a larger or more distant audience. In some cases, a sound reinforcement system may also be used to enhance the sound coming from sources on stage, rather than simply unaltered amplification of them.
A sound reinforcement system can be very complex, including hundreds of microphones, complex audio mixing and signal processing systems, thousands of watts of amplification power, and multiple speaker arrays, all supervised by a team of audio engineers and technicians. On the other hand, a sound reinforcement system can be as simple as a small PA (public address) system, which consists of a single microphone connected to a powered speaker for, say, a guitarist-singer playing in a coffee shop. In both cases, these systems reinforce the sound to make it louder or to distribute it to a larger audience.
Some audio engineers and others in the professional audio industry disagree about whether these audio systems should be called sound reinforcement systems or PA systems. The distinction given between the two terms according to technology and capacity is common, while others distinguish the intended use since, for example, reinforcement systems (SR) are made for support of live events and PA systems for the reproduction of speeches and recorded music in buildings and institutions. In some regions or markets, the distinction between the two terms is important, although the terms are considered interchangeable in many professional circles.
Basic concept
A typical sound reinforcement system consists of: input transducers (can be microphones), which convert sound energy into an electrical signal; signal processors, which alter the characteristics of the signal (equalizers, compressors, etc.); amplifiers, which boost the signal without changing its content; and finally, output transducers (speakers), which convert the signal back into sound energy. These primary parts include varying amounts of individual components to achieve the desired goal of reinforcing and clarifying the sound to the audience, performers, and other individuals.
Signal Path
Sound reinforcement in a large format system typically involves a signal starting with an instrument pickup or microphone (transducer), which is connected to a multicore cable (also called "snake"). The snake sends the signals from all the inputs to two mixing consoles: one in the "room" (FOH) for the main mix, and a monitor mix on a table next to the stage. Once the signal is on a channel in the console, it can be equalized, compressed, or panned before being sent to an output bus. The signal can also be sent to an external effects processor, which produces a 'wet' version of the signal. (with effects) of the signal, which in turn is mixed in varying amounts with the "dry" (no effects).
The signal is then sent to a bus, also known as a "mix group", "subgroup" or simply "group". A group of signals can be sent through an additional bus before being sent to the main bus to allow the engineer to control the levels of several related signals at the same time. For example, the various mics for a drum set can be sent to their own bus so that the volume of the entire set's sound can be controlled with a single fader or pair of faders. Sometimes a bus can be processed as as a single input channel, allowing the engineer to process an entire group of signals in a single display. The signal is then commonly routed with everything else to the master channel on the console. Mixing consoles have additional sends, also called auxiliaries or aux sends, on each input channel, so that a different mix can be created and sent elsewhere. One function of the aux sends is to create a mix of vocal and instrumental signals for monitoring (which singers or musicians hear onstage through their monitor speakers or in-ear monitors).
The next step in the signal path generally depends on the size of the system in the venue. In smaller systems, the main outputs are usually sent to an additional equalizer or directly to a power amplifier, with one or more speakers (usually two) connected to that amplifier afterwards. In large format systems, the signal is typically sent first to an equalizer and then to a crossover. A crossover splits the signal into multiple frequency bands and sends each to separate amplifiers and attached speakers for reproduction of low, mid, and high frequencies. Low frequencies are sent to amplifiers and then to subwoofers, while sounds in the mid and high frequencies are commonly sent to amplifiers that drive full-range speakers.
System components
Inlet Transducers
Many types of transducers can be found in a sound reinforcement system, with microphones being the most commonly used input devices. These can be classified according to their transduction method, their polar pattern, or their functional application. Most of the microphones used in sound reinforcement are dynamic and condenser microphones.
Microphones used for sound reinforcement are typically positioned and mounted in a variety of ways, including weighted stand stands, podium stands, clamps, instrument mounts, and headset assemblies. Headset and clip-mounted microphones are often used via wireless transmission to allow performers or speakers to move freely. Early adopters of headphone-mounted microphone technology include country singer Garth Brooks, Kate Bush, and Madonna.
There are many other types of input transducers, which may be used occasionally, including magnetic piezoelectrics used in electric guitars and electric basses, ceramic microphones for stringed instruments, and phonograph and piano pickups (cartridges) used in turntables. Wireless technology has become popular in sound reinforcement, commonly used for electric guitars, electric bass, and handheld microphones. This allows performers to move around the stage during the show or even into the audience without the worry of tripping or unplugging.
Mixing Consoles
Mixing consoles are the foundation of a sound reinforcement system. This is the place where the operator can mix, equalize, and add effects to signals coming from sound sources. Multiple consoles can be used for different applications in a single reinforcement system. The FOH can be placed where the operator can see the action on stage and hear the output of the speaker system. Some venues with permanently installed systems, such as religious facilities and theaters, place the mixer within an enclosed canopy, although this approach is more common for broadcast and recording applications. This is less common in live sound reproduction, as the engineer gets better results when he can hear what the audience is hearing.
Larger music productions often use a separate stage monitor mixer, which is dedicated to creating mixes on stage or in the ears of the performers. These consoles are generally placed at the side of the stage so that the operator can communicate with the performers. In cases where the performers have to play in a venue that does not have a monitoring engineer nearby from the stage, the monitor mix is done by the console engineer at the FOH, which is located in the audience or at the back of the concert hall. This arrangement can be problematic because performers end up asking for changes to the monitor mix via "hand signals and code phrases." The engineer also cannot hear the changes he is making to the monitors on stage, which almost always result in reduced mix quality.
Signal processors
Small PA systems for venues such as bars and clubs now feature features once only available to professional gear, such as reverb effects, graphic equalizers, and, on some models, feedback prevention circuitry with electronic sensors that prevent "squeaks" before they become a problem for the event. Digital effects units can offer multiple preset effects, such as variable reverb and echo. Digital speaker drive systems offer sound engineers digital delay, limiting, crossover functions, filters and EQs, compression and other functions in a simple 'rack-mountable' unit. In previous decades, sound engineers commonly had to transport a substantial number of rack-mounted analog peripheral devices to complete these tasks.
Equalizers
Equalizers exist in sound reinforcement systems in two forms: graphic and parametric. A high pass and/or a low pass filter may be included. Parametric EQs are often included on each channel in the mixer, although they can also be found separately in separate units. These first became popular in the 1970's and have remained the equalizer of choice for many engineers ever since.
Graphic equalizers contain faders (slide controls), which when placed together resemble a frequency response curve plotted on a graph. Sound reinforcement systems typically use graphic equalizers with center frequency control points in thirds of an octave. These are typically used to equalize audio signals going to the main speaker system or stage monitors.
Low pass (low cut) and high pass (high cut) filters restrict the bandwidth of a certain channel. By cutting the energy of very low frequencies (whose term is infrasonic or subsonic, the latter being not very appropriate) it reduces the waste of amplification power that does not produce audible vibration and that can also be harmful to the speakers. A low-pass filter to reduce ultrasonic energy is useful in preventing interference from radio frequency, lighting control, or digital circuitry near the amplifiers. Such filters are often included with graphic and parametric equalizers, providing complete control of the audible frequency range. If the response of these is steep enough, the high-pass and low-pass filters function as extreme cutoff filters. A feedback suppressor is an automatically tuned band-reject filter, also known as a notch filter, which includes a microprocessor that detects the beginning of the feedback and controls the filter so that it can suppress it by decreasing the gain along with the offending frequency.
Compressors
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Compressors are designed to manipulate the dynamic range of an audio signal. A compressor achieves this by reducing the gain of a signal that exceeds a defined intensity level (threshold) by a certain defined amount (ratio). Without gain reduction, a signal that reaches, for example, 10% more level at the input will produce a 10% increase at the output as well. Through reduction, a signal that exceeds a certain input level by this proportion will be louder, for example, by only 3% at the output. Most available compressors are designed to allow the operator to select a ratio within a range, typically between 1:1 and 20:1, while some even allow settings down to ∞:1. A compressor with an infinite ratio is typically known as a limiter. The speed at which the compressor adjusts the gain of the signal (called the "attack") can usually be adjusted, as is the final output of the device (gain).
Compressor applications vary widely, from objective system design standards to subjective applications determined by irregularities in show materials and engineer preferences. Some system design criteria specify the use of limiters for component protection and control of the gain structure. Artistic signal manipulation is a subjective technique widely used by mixing engineers to improve clarity or creatively alter the signal in relation to program material. An artistic example of compression is the serious compression commonly used in various components of a modern rock drum kit. Drums are processed to be perceived as punchier and fuller.
Noise Gates
A noise gate works by establishing a threshold in which if the signal is less than this, it will not let the signal through and, if this is stronger, the mechanism will allow the gate to open. The function of a noise gate is, in a sense, the opposite of that of the compressor. Noise gates are useful for microphones that pick up noise that is not relevant to the program material, such as the hum of a miked electric amplifier or the rustle of papers at the minister's podium.
Gatings are also used to process microphones placed next to drum parts in an ensemble in many rock and metal bands. Without a noise gate, the microphone of a specific instrument such as a floor tom will also pick up a signal from some other percussion or cymbal. By means of a noise gate, the sensitivity threshold for each microphone in the ensemble can be adjusted so that only the direct attack and decay of the intended instrument are heard, not nearby sounds.
Effects
Reverb and delay effects are widely used in sound reinforcement systems to enhance the mix relatively to the desired artistic impact of show material. Modulation effects such as flanger, phaser or chorus are also applied to some instruments. An exciter animates the sound of an audio signal by applying dynamic equalization, phase manipulation, and harmonic synthesis to typically high-frequency signals.
The appropriate type, variation, and level of effects is quite subjective and is often determined collectively by the production engineer, artist, or music director. Reverb, for example, can make the signal seem to be present anywhere, from a small room to a massive stadium, or even one that doesn't exist in the physical world. The use of reverb almost always goes unnoticed by the audience, as it usually sounds more natural than if the signal were 'dry'. The use of effects in modern music playback is often a problem. attempt to imitate the sound of the studio version of the artist's music.
Feedback Suppressor
A feedback suppressor detects acoustic feedback and normally removes it by inserting a filter notch into the system's signal path, which prevents "squeals" from occurring.
Power amplifiers
Power amplifiers increase the level of a minimum voltage signal and provide electrical power to enable the use of loudspeakers. All loudspeakers require power to amplify a signal with low amplitude, including headphones. Most professional amplifiers also provide protection from clipping signals, short circuits across the output, and excessive temperature. A limiter is often used to protect speakers from being overloaded.
As with most sound reinforcement equipment, professional amplifiers are designed to be mounted in standard 19-inch racks. Many power amps contain internal fans to draw air across their heat sinks. Since these can generate a significant amount of heat, heat dissipation is an important factor that operators consider when mounting amplifiers in racks. Active loudspeakers are characterized by internally mounted amplifiers, which have been selected by the manufacturer. to be the most suitable for the given speaker.
In the 70's and 80's, most amps were heavy, AB type. In the late 1990's these became lighter, smaller, more powerful, and more efficient, due to the increasing use of switching power supplies and D-type amplifiers, which offer significant weight and space savings, along with with higher efficiency. When installed in railway stations, stadiums and airports, their high efficiency allows them to operate with minimal additional cooling and higher rack module density compared to previous amplifiers.
Digital Loudspeaker Management Systems (DLMS) that combine crossover, compression, limiting, and other features into a single unit have become popular since their introduction. These are used to process the mix from the mixer and send it to various powered amplifiers. Systems can include many speakers, each with its own output optimized for a specific range of frequencies (low, mid, and high). Double, triple or quad amplification in a sound reinforcement system with the help of a DLMS results in more efficient use of amplification power by sending the appropriate frequencies to their respective loudspeaker. Most DLMS units that are designed for non-professional use have calibration and test functions such as a pink noise generator coupled with a real-time analyzer in order to perform automated room equalization.
The amount of amplified power used in a music performance installation depends on a number of factors, such as the desired Sound Pressure Level, whether the venue is indoors or outdoors, and the presence of ambient noise. troubled. The following list provides a "rule of thumb" Approximate estimate for the amount of amplification power used in different installations:
- Small vocal system- About 500 watts
- Large vocal system - About 1,000 watts
- Small local system - 9,000 watts
- "Great local system" - About 18,000 watts
- "Stage System" - About 28,000 watts
Output Transducers
Main speakers
A simple, inexpensive loudspeaker for a PA system may contain a full-range loudspeaker driver, embedded in a suitable enclosure. Professionally calibrated sound reinforcement speakers may incorporate separate drivers to produce sounds at low, mid, and high frequencies. A crossover network sends the different frequencies to the appropriate controllers. In the 1960's, the horn speakers found in theaters and PA systems were almost always 'columns' of multiple drivers mounted in a vertical line within a tall container. The 1970's and early 1980's was a period of innovation in speaker design with multiple sound reinforcement companies designing their own speakers. The basic designs were based on others already known and the loudspeaker components were obtained from others already commercial.
The areas of innovation were in the design of the showcases, the durability, the ease of packing and transportation, and the simplicity of its configuration. This period also saw the introduction of the hanging or "flight" of the main speakers at large concerts. During the 80's, manufacturers of large loudspeakers began to produce standard equipment using the innovations of the 70's. These were mostly two-way systems with 12-inch, 15-inch, or 30-inch woofers and a high-frequency driver attached to a speaker with this range. The 1980's also saw the start of companies focused on the sound reinforcement market. The 1990's saw the introduction of the 'Line array', in which long vertical arrays of loudspeakers with a small cabinet were used to increase efficiency and provide uniform dispersion and frequency response.. This period was also marked by the introduction of inexpensive molded plastic speaker containers mounted on tripods. Many of these are characterized by their built-in power amplifiers, which made them practical for non-professional use in terms of installation and successful operation. The sound quality available from these simple "powered speakers" varies widely depending on the implementation.
Many sound reinforcement speaker systems incorporate protection circuitry, which prevents damage from excess power or misoperation. Positive temperature coefficient resistors, specialized current-limiting light bulbs, and switches were used alone or in combination to reduce failure. During the same period, the professional sound reinforcement industry made the Speakon NL4 and NL8 connectors from Neutrik brand became the standard input connectors, replacing Cannon's one-inch jacks, XLR connectors, and multi-pin connectors, which are limited to a 15 amps maximum current. XLR connectors are still the standard for input connectors in active speaker cabinets.
The three different types of transducers are subwoofers, compression drivers, and tweeters. All of them are characterized by the combination of a voice coil, a magnet, a cone or diaphragm and a shell or structure. Loudspeakers have a power rating (in watts), which indicates their maximum power capacity, to help users avoid feeding them with more power than is necessary for proper operation. Thanks to the efforts of the Audio Engineering Society (AES) and loudspeaker industry group ALMA, power handling specifications have become more reliable, although adoption of the EIA-426-B standard is still far from universal. Around the mid 90's, trapezoidal shaped containers became popular, as this shape allowed many of them to be easily arranged together.
A number of companies are now making lightweight, portable speaker systems for small venues that send part of the low frequencies in music (electric bass, kick drum, etc.) to a powered subwoofer. Sending the low-frequency energy to a separate amplifier can substantially improve the low-end response of the system. Furthermore, clarity can be improved, because sounds at low frequencies consume a large part of the amplification power; With only a single amplifier for the audible spectrum, hungry low-frequency sounds can consume a disproportionate amount of the reinforcement system's power.
Professional sound reinforcement speaker systems continually include dedicated hardware to "fly away" over the stage area to provide more uniform coverage and maximize visibility within music venues.
The number of speaker cabinets used in a performance varies considerably, although the following list provides a rough idea of how many are used in a typical venue:
- Little vocal system. Two full range speakers mounted on tripods.
- Large vocal system -Four full range speakers for wide spatial coverage.
- "Local system" small - Two subwoofers and two speakers of medium and high frequencies.
- "Great local system" - Four subwoofers and four speakers of medium and high frequencies.
- "Stage System" small - Four subwoofers, four speakers of low average frequencies and four of high mean frequencies.
Monitors
Monitors, also called stage speakers, are speakers used onstage to help performers hear their singing or playing. As such, the monitors are directed towards a performer or a section of the stage. They are usually fed a different mix of vocals or instruments than is fed to the main speaker system. Monitors are often wedge-shaped, directing their output upward toward the performer when placed on the stage floor. Designs with dual two-way drivers with a speaker cone and a horn are common, as the monitors need to be smaller to save stage space. These speakers generally require less power and volume than the main speaker system, since they only provide sound for a few people who are in relatively close proximity to them. Some manufacturers have designed speakers for use as components of a small PA system or as monitors. In the past decade, a number of these have produced powered stage speakers, which contain an integrated amplifier.
Using stage speakers instead of in-ear monitors typically results in increased volume onstage, which can lead to further acoustic feedback problems and hearing damage for performers in front of you. them. The clarity of the mix for the performer on stage is also not optimal due to extraneous noise from the surroundings. Using the monitor, active (with an integrated amplifier) or passive, requires more cabling and stage equipment, resulting in an even messier rig. These factors, along with others, have led to the increase in popularity of in-ear monitors.
In-Ear Monitors
In-ear monitors are headphones that have been designed for use as monitors by a live performer. These can be of universal design or tailored to the user. Universally designed monitors have rubber or foam tips that can be inserted into virtually anyone's ear. Custom designs are created from the client's earmold, which is made by an audiologist. In-ear monitors are almost always used in conjunction with a wireless transmission system, allowing the performer to move freely around the stage while their monitor mix is maintained.
Monitors in ear offer considerable isolation for the performer using them, which means that the monitor engineer can craft a much clearer and more accurate mix for himself. Through the in-ear monitors, each performer can be sent their own individual mix; while this was also the case with stage monitors, a performer's ear monitors cannot be heard by other musicians. A disadvantage of this isolation is that the performer cannot hear the audience or others on stages that do not have microphones (for example, a bass player). This has been solved in large productions by installing two microphones facing the audience on each side of the stage that are mixed into the feeds to the in-ear monitors.
Since their introduction in the mid-'80's, in-ear monitors have grown to be the most popular monitoring option for large touring gigs. The reduction or elimination of non-instrument amp speakers onstage has allowed for a clearer environment and fewer mix-related issues for both floor and monitor engineers. Feedback is easier to deal with, and there are fewer acoustic reflections from the rear walls of the stage toward the audience, affecting the clarity of the mix the floor engineer is trying to create.
Applications
Sound reinforcement systems are used in a wide range of different settings and venues, each facing different challenges.
Systems for rent
AV rental systems have to be able to withstand rough use and even abuse by renters. For this reason, rental companies tend to keep speakers that are tightly wrapped and protected with steel corners, and electronic equipment such as power amps or effects mounted inside protective shipping cases. Likewise, these companies tend to select accessories that have electronic protection features, such as speaker protection circuitry and amplifier limiters.
Similarly, non-professional rental systems need to be easy to use and install, and easy to service and maintain by the company. From this perspective, loudspeakers require easily accessible horns, speakers, and crossover circuits in order that repairs or replacements can be made. Some rental companies often rent self-powered console-amps, mixers with onboard effects, and powered subwoofers for non-professional use, which are easier to set up and use.
Many touring concerts and corporate events at large venues rent large sound reinforcement systems that typically include one or more staff audio engineers from the renting company. In the case of touring rental systems, there are typically several engineers and technicians from the rental company who travel with the show to set up and calibrate the equipment for use by the band's production staff. The subject that will carry out the mix is usually selected and provided by the band, since this is a person who has become familiar with aspects of the show and has worked on the spot to establish a general idea of what they want the show to sound like.. The show's mixing engineer sometimes also happens to be on staff at the rental company selected to provide equipment for the tour.
Live music clubs
Installing sound reinforcement for live music clubs often presents unique challenges, as there are a wide variety of venues that are used as clubs, ranging from old warehouses or musical theaters to small restaurants or walled basement taverns of concrete. In some cases, clubs are housed in multi-story venues, with balconies, or in "L"-shaped rooms, making it difficult to get a consistent sound for all audience members. The solution is to use fill speakers to get good coverage, using a delay (effect) to make sure the audience doesn't hear the same sound at different times.
Another problem with designing sound systems for live music clubs is that the sound system might need to be used for both pre-recorded music being played by DJs and live performances. IF the sound system is optimized for pre-recorded DJ music, then it will not provide the appropriate sonic qualities (or monitoring and mixing equipment) needed for live music and vice versa. Finally, live music clubs can be a hostile environment for sound equipment, as the air can be hot, humid, and smoky; in some clubs, keeping power amp racks cool can be a challenge. Usually, an air-conditioned room just for the amplifiers is used.
Sound for church.
Designing systems for churches and similar religious facilities is also challenging, as loudspeakers may need to be inconspicuous when combined with antique wood and stone work. In some cases, audio designers have gone so far as to create custom-painted speakers so that the speakers fit properly into the architecture of the church. Some religious sites, such as shrines or chapels, are long rooms with low ceilings, which means that additional reinforcement speakers are needed throughout the entire space to provide good coverage. An additional challenge with church sound reinforcement systems is that, once installed, they are almost always operated by lay volunteers from the congregation, which means that they must be easy to operate and related technical problems must be easily as well. resolved.
Some mixing consoles designed for temples contain automatic faders, which turn off unused channels to reduce noise, and kill circuitry that detects and removes frequencies that are causing feedback. These features may also be available in multi-function consoles used in convention facilities and other multi-purpose venues.
Systems for tours
Sound systems for tours need to be powerful and versatile enough to cover many types of venues, often of different sizes and shapes. These also need to use "field replaceable" such as speakers, horns and fuses, which are easily accessible for repair during a concert program. Sound systems for tours are commonly designed with redundancy features, so that in the event of equipment failure or amplifier overheating the system will continue to function. Touring systems for shows performed for crowds of a few thousand people and more are typically installed and operated by a team of technicians and engineers who travel with the talent to each event.
It is not uncommon for popular concerts to be played in medium to large-sized venues during the tour to schedule one to two weeks of technical rehearsal with the full set for the concert and production staff present. This allows audio and lighting engineers to become familiar with the show and pre-set digital equipment for each part of the event, if necessary. Many modern bands work with FOH and monitor engineers during this time to establish their general idea of what the show should sound like, both to themselves and to the audience. This often involves programming different effects and digital processing for use on specific songs, in an attempt to make them sound somewhat similar to the studio versions. To handle the show with many of these types of changes, mixing engineers often choose to use a digital mixing console, so that they can remember these settings between songs. Technicians are kept busy during the event, making sure the SR system is operating properly and is calibrated correctly, as the acoustic response of a venue will respond differently throughout the day depending on temperature, humidity, and number of people. in the room.
PA systems for weekend bands are a niche market for touring sound reinforcement equipment. These bands need systems that are small enough to fit in a minivan or the trunk of a car, yet powerful enough to provide adequate, even dispersion of sound, along with acceptable vocal intelligibility for a noisy club or bar.. In the same way, the systems need to be easy and quick to install. Sound reinforcement companies have responded to this demand by offering equipment that fills multiple roles, such as powered mixers (a mixer with a built-in power amp and effects) and powered subwoofers (a subwoofer with a power amplifier and integrated crossover). These products minimize the number of connections bands have to make to install the system. Some subwoofers contain brackets on top, so these can do double duty by also serving as a base for full-range PA speakers mounted on this bracket.
Live theater
Sound for live theatre, opera house and other dramatic applications can present problems similar to those in churches, in cases where the theater is part of a heritage/historic building where speakers and cabling might need to be mixed with lumber jobs The need for clear lines of sight in some theaters may make the use of regular loudspeakers unacceptable; instead, compact, low-profile loudspeakers are frequently used.
In live theater and any drama, performers move around the stage, which means wireless microphones must be used. These need to be properly installed and cared for, to avoid interference and reception problems.
Some big-budget stage shows and musicals are mixed in live surround sound, in which the on-site sound operator often 'shoots' the sound. sound effects that are mixed with music and dialogue by the show's mixing engineer. Designs in these systems are usually more extensive, often involving a separate set of loudspeakers for different zones in the theater.
Classical music and opera
A delicate type of sound reinforcement called acoustic enhancement is used in some concert halls where works of classical music, such as symphonies and operas, are performed. Acoustic enhancement systems help provide a more uniform sound in the room and prevent "dead spots" in the seating area by "increasing the intrinsic acoustic characteristics of the room." The systems use "...an array of microphones connected to a computer [which are] connected to an array of speakers". However, as attendees have become aware of the use of these systems, debates have arisen, as "...purists insist that the natural acoustic sound of [classical] voices [or] instruments in a given room must not be disturbed".
Kai Harada's article Opera's Dirty Little Secret states that opera houses have begun using electronic acoustic enhancement systems "... to compensate for the flaws in the acoustic architecture of a venue". Despite the outcry that has arisen among opera lovers, Harada points out that none of the opera houses that use acoustic enhancement systems "...use traditional Broadway-style sound reinforcement, in which most, if not all of the singers are rigged with radio microphones mixed into an array of unattractive speakers scattered throughout the theater". Instead, most opera houses use sound reinforcement systems to enhance the acoustics of the venue and for fine augmentation of offstage voices, lead dialogue, and sound effects (for example, church bells). in the Tosca opera or some thunder in Wagner operas).
Acoustic enhancement systems include LARES (Lexical Acoustic Enhancement and Reinforcement System) and SIAP (System for Improved Acoustic Interpretation). These systems use microphones, computer processing "with delay, phase and changes in frequency response" and then they send the signal "... to a large number of loudspeakers placed at the extremities of the venue for the performance." Another acoustic enhancement system called VRAS (Variable Room Acoustic System) uses "... different algorithms based on microphones placed around the room." The "Deutsche Staatsoper" in Berlin and the Hummingbird Center in Toronto use the LARES system. The Ahmanson Theater in Los Angeles, the Royal National Theater in London, and the Vivian Beaumont Theater in New York City use the SIAP system.
Reading rooms and conference rooms
Lecture rooms and conference rooms pose the challenge of reproducing speech clearly to a large audience, which may have echo-producing reflective surfaces. At some conferences, sound engineers have to provide microphones for a large number of people, in the case of a panel or debate conference. In some cases, automatic mixers are used to control microphone levels.
Sound systems for sports
Systems for outdoor sports facilities and ice rinks often have to deal with a substantial amount of echo, which can render speech unintelligible. Sports and recreational sound systems often face environmental challenges in the same way, such as the need for weatherproof outdoor speakers in stadiums, as well as splash and moisture resistant speakers in swimming pools.
Installation and testing
Large-scale sound reinforcement systems are designed, installed, and operated by audio engineers and audio technicians. During the design phase of a new venue, audio engineers work with architects and business owners to ensure that the proposed layout accommodates the loudspeakers and provides appropriate space for sound technicians and racks of audio equipment. Sound engineers also give advice on which audio components are best suited to the space and their intended use, as well as the proper placement and installation of these components. During the installation phase, sound engineers ensure that high-power electrical components are securely installed and connected, and that wall- or ceiling-mounted speakers are properly positioned (or 'blown').;) on the rig. When sound reinforcement components are installed, sound engineers test and calibrate the system so that its sound production is consistent across the frequency spectrum.
System test
A sound reinforcement system must be able to reproduce a signal from its input, through any processing, to its output without any coloration or distortion, all accurately. However, due to inconsistencies in size, shape, construction materials, and even crowd density, this is not always possible without prior calibration of the system. This can be done in many ways. The oldest method of system calibration involves a set of healthy ears, test program material (music or speech), a graphic equalizer, and last but not least, familiarity with the proper (or desired) frequency response.). You should listen to the program material through the system, take note of any changes in frequency or resonance, and subtly correct them through the use of an equalizer. Engineers skilled at this typically use a specific playlist of music each time they calibrate a system with which they should become familiar. This process is still used by many engineers, even when analysis equipment is used, such as to check how the system sounds with music or speech.
Another method of manual calibration requires a pair of high-quality headphones patched to the input signal before any processing (such as hearing before intervention of an input channel fader with the test program on the console). mixer, or with the headphone output of the CD player or on the cassette player). This direct signal can then be used as part of a near-perfect reference against which to find any differences in frequency response. This method may not be perfect, but it can be very useful when resources or time are limited, such as using pre-show music to correct for changes in response caused by audience arrival. Because this is a still very subjective method of calibration, since the human ear is very dynamic in its own response, the software material used for testing should be as similar as possible to that which the system will use in the event.
Since the development of digital signal processing (DSP), there have been many pieces of computer hardware and software designed to change the workload of the calibration system from human audit interpretation to computer algorithms running on microprocessors. A tool for calibrating a sound system using DSP or analog signal processing is a Real Time Analyzer (RTA). This tool is commonly used by sending pink noise into the system and measuring the result with a specially calibrated microphone attached to the RTA. By making use of this information, the system can be adjusted to meet the desired response. The response displayed by the RTA microphone cannot be taken as a true representation of the room, as the analysis will be different, sometimes drastically, when the microphone is placed in a different position in front of the system.
Recently, sound engineers have seen the introduction of dual FFT (Fast Fourier Transform) based audio analysis software, which allows the engineer to look at not only frequency versus amplitude (pitch) information against volume) that an RTA provides, but also to see the same signals (sounds) in the time domain. This provides the engineer with much more meaningful data than an RTA alone. Additionally, dual FFT analysis allows you to compare the source signal to the output signal and see the difference. This is a very quick way to calibrate a system to sound as close as possible to the original source material. As with any measurement tool, this must always be verified by means of real human ears. Some DSP system processing devices have been designed for use by non-professionals, so they automatically make system equalizer adjustments based on the RTA microphone reading. These are almost never used by professionals, since they almost never calibrate the system optimally as professional audio engineers do manually.