As with most recording sessions, the quality depends on the location, microphone technique and ambient noise level. The recording of the impulse can directly be used in a convolution software. The advantage of using a transient sound (starter pistol, clapper board, balloon) is that there is no need for any post processing. Anything that is loud and creates a broadband burst of noise will do. Transient method: The second most common method and perhaps the easiest is to use a starter pistol, balloon or clapper board (especially on location for a shoot).The sweep is played off a speaker to excite the space (here’s more information about the sweep on ). The longer the length, the greater the signal-to-noise ratio but also greater the chance of recording resonances/noisy vibrations in a space. Depending on the length of the sweep, it usually provides the best signal-to-noise ratio. Sine sweep: A sine sweep is the most preferred method to record an impulse response.To record an IR, you need a sound (source) to excite the space and some recording equipment (obviously!). Anything that alters sound and is excitable!.Spaces (including different perspectives).Eg: convolving the sound of a synth with a drumkit to create a ‘rhythmic-synth’. It is also quite common to import non-IR files into convolution software. The IRs themselves can be manipulated in a DAW (before being imported into the convolution plugin/software) to create an even greater library of interesting sounds. A single IR can be used to create a fresh library of sounds out of existing recordings. The convolution process is also useful for designing interesting sounds by using IRs of objects like tin cans, plastic buckets, bottles or any sound altering device. It has proved to be extremely useful in post-production where it is important to re-create believable spaces, match ADR to location sound and in creating believable perspectives in the mix. It is common to find IRs of famous venues from around the world or even vintage gear. The immediate use of IRs is to recreate real world spaces. Some convolution plugins like Altiverb and Waves IR-1 use proprietary formats, although they are capable of importing regular WAV or AIFF files as well. The recorded IR is nothing more an audio file that can be imported into a convolution software to recreate the sampled space digitally. For more accurate results it is common to use a sine-sweep across the audible frequency range. This is achieved by playing back a burst (impulse) of a full range of frequencies within the space and recording it. The impulse responses or IRs are captured by recording how a space responds to a full range of frequencies (typically 20Hz to 20,000Hz). It could be described as an acoustic ‘photograph’, where, instead of capturing a space visually, it is captured aurally. Impulse responses allow us to capture and store the acoustic characteristics of a space (or piece of sound altering equipment). Over the recent years, convolution has been widely used to recreate the reverberation of spaces, the sound of hardware units (reverb units, equalisers, tape machines, guitar amps, etc) and in creative sound design. Convolution of spectra means that each point in the discrete frequency spectrum of input a is convolved with every point in the spectrum b. It is different from the plain multiplication of two sounds where a single sample of the first sound is multiplied by the corresponding single sample of a second sound.Ĭurtis Roads ( The Computer Music Tutorial) describes convolution as:Ĭonvolution of two audio signals is equivalent to filtering the spectrum of one sound by the spectrum of another sound. What is convolution?Ĭonvolution is the process where a single sample of a sound is multiplied by every sample of another sound. This article is a description of the general concepts behind recording good impulse responses and should be easily adaptable to any convolution/de-convolution tool. This not only helps ‘personalise’ your mixes, but is extremely useful in post-production and in the design of new sounds.Įach of the above mentioned plugins need slightly different techniques for creating a custom library of impulse responses. They are usually packaged with large and useful libraries of impulse responses (more on what all this means below), but what makes them really powerful is the fact that it is quite easy to record and use your own impulse responses. Some of the most common ones include Audio Ease Altiverb, Logic’s Space Designer, Avid TL Space, Waves IR-1 and McDsp Revolver. With growing computing power over the last decade, convolution plugins have become commonplace.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |