Reverberation

Reverberation Reverberation is the continuation of a particular sound after the original sound is removed. When sound is produced in a space, a large number of echoes build up and then slowly decay as the sound is absorbed by the walls and air, creating reverberation, or reverb. This is most noticeable when the sound source stops but the reflections off walls, curtains, carpets etc continue, decreasing in volume until they can no longer be heard. A reflected sound wave like this will arrive a little later than the direct sound, since it travels a longer distance, and is generally a little weaker, as the walls and other surfaces in the room will absorb some of the sound energy. Shortly after the direct sound, the reverberant sound arrives. The time between the two is called the 'arrival time gap'. This gap is important in recorded music because it is the cue that gives the ear information on the size of the hall, better digital reverbs can incorporate this arrival time gap and hence sound more realistic. Chamber reverberators The first reverb effects were created by placing a loud speaker and a microphone in a real space such as a hall using that space as a natural echo chamber. The mike would pick up the sound from the speaker including the reverberated sound. To make the effect stronger the walls of the room are covered with sound-reflecting discs or other similar materials. By changing the position of the speaker and the microphone it is possible to get some variations in a recorded sound. The down side of this technique is that it is difficult to vary the reverb time. Plate reverberators A plate reverb system uses an electromechanical transducer. The transducer is a device which converts electrical voltage variations representing music or speech, to mechanical vibration. The transducer creates vibration in a large plate of sheet metal. A pickup captures the vibrations as they bounce across the plate, and the result is output as an audio signal. It was possible to control time of oscillations of such plate using damping. Damping means the quieting or abrupt silencing of the plate. Spring reverberators Above - home made spring reverb. Spring reverberators were once widely used in semi-professional recordings due to their modest cost and small size. Using vocals through the toy echo microphones you can buy gives you an idea what a spring reverb sounds like. One end of the spring had an electromagnetic transducer that made it oscillate and the other end had a sound-receiver that picked up the vibrations. The sound is of a lower quality than plate reverbs, but the devices are small enough to fit inside guitar amplifiers. Digital reverberators Mirochips work out the mathematics in complex algorithms (a sequence of instructions) to produce somewhat accurate reverberation for any environment. On today's high end reverb units an engineer has the option to program in the exact dimensions of the "room" he wishes to use for digital reverb. Reverberation is produced caused by a very large number of echoes, simple digital signal processors use multiple feedback delay to create a large, decaying series of echoes that die out over time. Trigger the multistage analog delay chip at a very short delay, and layer these with other such short delays, and a reverb effect is produced. Digital reverb is basically a simulation of the spring, creating a more accurate type of reverb. Cheap reverb units fail to create a good enough sound. The more expensive ones have software that carefully simulates typical rooms, - the space, the absorption etc. ‘Plug -in’ Reverbs A reverb ‘plug in ‘is the software equivalent of digital reverb hardware they don't make sound themselves, they change a sound that already exists. For a plugin you need a digital audio "host application". There are two types of audio host apps: • Multitrack studios: eg Cakewalk SONAR, Steinberg Cubase, Emagic Logic (and many more)... These apps are like a multitrack tape recorder - you record several parts and then mix them together into a final production. • Audio editors: eg Sonic Foundry Sound Forge, Syntrillium Cool Edit Pro, Steinberg Wavelab (etc)... These are for editing individual WAV files - cutting, fading, splicing etc. • The Steinberg products use a technology called VST, the others use one called DirectX. In each case it allows the application to have more "options" available in their menus There are two ways you can use these effects: • Destructively - you perform an "edit" in which you apply the effect. The audio is modified by the operation; • Non-destructively - you "plug" the effect in the chain, and the audio passes through it before you hear it. The original audio is not modified by this operation . Convolution Reverb A Convolution Reverb consists of a recorded sample (called an Impulse Response or "IR") of an acoustic space such as a hall. A signal such as a starter gun, or snare drum crack, and the effect on the space of that signal after it has been removed and usably transformed by the convolution processor. Convolution reverbs record and process the reverberant effect unique to a real acoustic space. Convolution reverbs are so-called because the sequence of signal "events" is reversed: A space is excited by a signal and recorded, and the resulting sound or ambience of that space is then processed and used to treat and react to an entirely different signal. The original convolution reverbs were fantastic-sounding but very expensive hardware boxes, and as such largely an elite studio commodity. By now this technology is available as computer software at a fraction of the original cost, and may be used the same way any other DSP plug-in is used in signal processing. In short, you can sample your favorite cave, closet, or garbage can and use it as a reverb effect on a lead vocal or acoustic guitar track recorded in your software of choice. Or, you can simply select a preset from the large sampled-space libraries that accompany most convolution reverb packages. The convolution reverb processor can be found in both hardware and software plugin effects Year Reverb Device Pre 1930’s 1930’s 1957 Iate 1970’s 1990’s to present Reverb chambers Spring reverb Plate reverb Digital reverb Software ‘plug in’ reverb 2000 Convolution reverb Reverberation Reverberation is the continuation of a particular sound after the original sound is removed. When sound is produced in a space, a large number of echoes build up and then slowly decay as the sound is absorbed by the walls and air, creating reverberation, or reverb. This is most noticeable when the sound source stops but the reflections off walls, curtains, carpets etc continue, decreasing in volume until they can no longer be heard. A reflected sound wave like this will arrive a little later than the direct sound, since it travels a longer distance, and is generally a little weaker, as the walls and other surfaces in the room will absorb some of the sound energy. Shortly after the direct sound, the reverberant sound arrives. The time between the two is called the 'arrival time gap'. This gap is important in recorded music because it is the cue that gives the ear information on the size of the hall, better digital reverbs can incorporate this arrival time gap and hence sound more realistic. Chamber reverberators The first reverb effects were created by placing a loud speaker and a microphone in a real space such as a hall using that space as a natural echo chamber. The mike would pick up the sound from the speaker including the reverberated sound. To make the effect stronger the walls of the room are covered with sound-reflecting discs or other similar materials. By changing the position of the speaker and the microphone it is possible to get some variations in a recorded sound. The down side of this technique is that it is difficult to vary the reverb time. Plate reverberators A plate reverb system uses an electromechanical transducer. The transducer is a device which converts electrical voltage variations representing music or speech, to mechanical vibration. The transducer creates vibration in a large plate of sheet metal. A pickup captures the vibrations as they bounce across the plate, and the result is output as an audio signal. It was possible to control time of oscillations of such plate using damping. Damping means the quieting or abrupt silencing of the plate. Spring reverberators Above - home made spring reverb. Spring reverberators were once widely used in semi-professional recordings due to their modest cost and small size. Using vocals through the toy echo microphones you can buy gives you an idea what a spring reverb sounds like. One end of the spring had an electromagnetic transducer that made it oscillate and the other end had a sound-receiver that picked up the vibrations. The sound is of a lower quality than plate reverbs, but the devices are small enough to fit inside guitar amplifiers. Digital reverberators Mirochips work out the mathematics in complex algorithms (a sequence of instructions) to produce somewhat accurate reverberation for any environment. On today's high end reverb units an engineer has the option to program in the exact dimensions of the "room" he wishes to use for digital reverb. Reverberation is produced caused by a very large number of echoes, simple digital signal processors use multiple feedback delay to create a large, decaying series of echoes that die out over time. Trigger the multistage analog delay chip at a very short delay, and layer these with other such short delays, and a reverb effect is produced. Digital reverb is basically a simulation of the spring, creating a more accurate type of reverb. Cheap reverb units fail to create a good enough sound. The more expensive ones have software that carefully simulates typical rooms, - the space, the absorption etc. ‘Plug -in’ Reverbs A reverb ‘plug in ‘is the software equivalent of digital reverb hardware they don't make sound themselves, they change a sound that already exists. For a plugin you need a digital audio "host application". There are two types of audio host apps: • Multitrack studios: eg Cakewalk SONAR, Steinberg Cubase, Emagic Logic (and many more)... These apps are like a multitrack tape recorder - you record several parts and then mix them together into a final production. • Audio editors: eg Sonic Foundry Sound Forge, Syntrillium Cool Edit Pro, Steinberg Wavelab • The Steinberg products use a technology called VST, the others use one called DirectX. In each case it allows the application to have more "options" available in their menus There are two ways you can use these effects: • Destructively - you perform an "edit" in which you apply the effect. The audio is modified by the operation; • Non-destructively - you "plug" the effect in the chain, and the audio passes through it before you hear it. The original audio is not modified by this operation . (etc)... These are for editing individual WAV files - cutting, fading, splicing etc. Convolution Reverb A Convolution Reverb consists of a recorded sample (called an Impulse Response or "IR") of an acoustic space such as a hall. A signal such as a starter gun, or snare drum crack, and the effect on the space of that signal after it has been removed and usably transformed by the convolution processor. Convolution reverbs record and process the reverberant effect unique to a real acoustic space. Convolution reverbs are so-called because the sequence of signal "events" is reversed: A space is excited by a signal and recorded, and the resulting sound or ambience of that space is then processed and used to treat and react to an entirely different signal. The original convolution reverbs were fantastic-sounding but very expensive hardware boxes, and as such largely an elite studio commodity. By now this technology is available as computer software at a fraction of the original cost, and may be used the same way any other DSP plug-in is used in signal processing. In short, you can sample your favorite cave, closet, or garbage can and use it as a reverb effect on a lead vocal or acoustic guitar track recorded in your software of choice. Or, you can simply select a preset from the large sampled-space libraries that accompany most convolution reverb packages. The convolution reverb processor can be found in both hardware and software plugin effects. Year Reverb Device Pre 1930’s 1930’s 1957 Iate 1970’s 1990’s to present Reverb chambers Spring reverb Plate reverb Digital reverb Software ‘plug in’ reverb 2000 Convolution reverb