Dereverberation is the process by which the effects of

reverberation Reverberation (also known as reverb), in acoustics, is a persistence of sound, after a sound is produced. Reverberation is created when a sound or signal is reflected causing numerous reflections to build up and then decay as the sound is abso ...

are removed from sound, after such reverberant sound has been picked up by

microphone A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publ ...

s. Dereverberation is a subtopic of acoustic

digital signal processing Digital signal processing (DSP) is the use of digital processing, such as by computers or more specialized digital signal processors, to perform a wide variety of signal processing operations. The digital signals processed in this manner are ...

and is most commonly applied to speech but also has relevance in some aspects of music processing. Dereverberation of audio (speech or music) is a corresponding function to

blind deconvolution In electrical engineering and applied mathematics, blind deconvolution is deconvolution without explicit knowledge of the impulse response function used in the convolution. This is usually achieved by making appropriate assumptions of the input to ...

of images, although the techniques used are usually very different. Reverberation itself is caused by sound reflections in a room (or other enclosed space) and is quantified by the room

reverberation time Reverberation (also known as reverb), in acoustics, is a persistence of sound, after a sound is produced. Reverberation is created when a sound or signal is reflected causing numerous reflections to build up and then decay as the sound is abso ...

and the direct-to-reverberant ratio. The effect of dereverberation is to increase the direct-to-reverberant ratio so that the sound is perceived as closer and clearer. A main application of dereverberation is in hands-free phones and desktop conferencing terminals because, in these cases, the microphones are not close to the source of sound – the talker’s mouth – but at arm’s length or further distance. As well as telecommunications, dereverberation is importantly applied in

automatic speech recognition Speech recognition is an interdisciplinary subfield of computer science and computational linguistics that develops methodologies and technologies that enable the recognition and translation of spoken language into text by computers with the ...

because speech recognizers are usually error-prone in reverberant scenarios. Dereverberation became established as a topic of scientific research in the years 2000 to 2005.,P. A. Naylor and N. D. Gaubitch, “Speech dereverberation,” in Proc. Intl. Workshop Acoust. Echo Noise Control (IWAENC), 2005.
/ref> although a few notable early articles exist.L. E. Ryall, "Improvements in electric signal amplifiers incorporating voice-operated devices", Patent GB509613A, 1938.
/ref> The first scientific text book on the topic was published in 2010.P. A. Naylor and N. D. Gaubitch, Eds., Speech Dereverberation. Springer, 2010.
/ref> A global scientific study sponsored by the

IEEE The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operati ...

Technical Committee for Audio and Acoustic Signal Processing took place in 2014.The REVERB Challenge
/ref> Three different approaches can be followedE. Habets, Fifty Years of Reverberation Reduction, Audio Engineering Society 60th Conference on Dereverberation and Reverberation of Audio Music and Speech
/ref> to perform dereverberation. In the first approach, reverberation is cancelled by exploiting a mathematical model of the acoustic system (or room) and, after estimation of the room acoustic model parameters, forming an estimate for the original signal. In the second approach, reverberation is suppressed by treating it as a type of (convolutional) noise and performing a de-noising process specifically adapted to reverberation. In the third approach, the original dereverberated signal is directly estimate from the microphone signals using, for example, a deep neural network machine learning approach or alternatively a multichannel linear filter. Examples of the most effective methods in the state-of-the art include approaches based on

linear prediction Linear prediction is a mathematical operation where future values of a discrete-time signal are estimated as a linear function of previous samples. In digital signal processing, linear prediction is often called linear predictive coding (LPC) and ...

A. Jukic et al., "Multi-Channel Linear Prediction-Based Speech Dereverberation With Sparse Priors"
/ref>M. Delcroix et al, Linear Prediction-based Dereverberation with Advanced Speech Enhancement and Recognition Technologies, REVERB Challenge Workshop, 2014
/ref>

References

{{reflist Digital signal processing Audio effects Acoustics