Acoustic Feedback

In technical devices, the reverse acoustic coupling phenomenon occurs as a result of self-excitation of the speaker system , for example, when the microphone amplifies the signal from the speaker (usually in the high frequency range), in small rooms due to reflection ^[2] or when using amplification equipment , when the loudspeaker sound causes the player's vibration , in the pickup, it is converted into an electrical signal reproduced by a loudspeaker, which causes the player to vibrate even more. Thus, a positive feedback loop occurs in which the vibration itself sustains, increasing more and more ^[3] .

The technique uses the abbreviation AFBS - Acoustic FeedBack System - acoustic feedback ^[4] .

In biology and medicine, acoustic feedback is referred to as Auditory Feedback . It is a type of biofeedback ^{[5] [6] [7] [8]} . It is considered an essential element in the programs of recognition, correction of speech and the development of skills of a professional speaker. There are five components of acoustic feedback: real-time amplification, reverse playback with delay, DAF (Delayed Auditory Feedback, delayed auditory feedback), masking (using frequency filters) sound ^[9] , tempo control ^[10] .

Altered Auditory Feedback - AAF ^[11] .

It is created with the help of special equipment to obtain the effect of eliminating speech breaks and developing smooth speech in persons suffering from stuttering .

DAF - Delayed Auditory Feedback ^[11] - delayed acoustic (more precisely, auditory) feedback - the arrival of a sound (in this case, speech) signal to a sound-receiving organ with an artificially created (hardware) delay, usually 40-220 milliseconds ^[12] .

Auto - DAF is a function of delayed acoustic feedback for the treatment of stuttering and logoneuroses, which automatically adjusts to the speech of each patient and automatically places the correct speech breathing ^[13] . It is calculated automatically according to a predetermined algorithm based on the results of digital processing of an acoustic signal. Used in specialized computer applications to eliminate speech disorders.

FAF - Frequency - Altered Auditory Feedback - verbatim - frequency-changed (in frequency) acoustic feedback ^[11] . Allows you to change the pitch of an audible speech. For the correction of speech disorders, the most effective use of FAF / DAF.

CAF - Conjugating Auditory Feedback - conjugating acoustic feedback. Connects low-frequency speech breaks that occur at the time of speech spasms ^[13] .

Experimentally analyzing sound — decomposing it into a spectrum of harmonic oscillations using a set of resonators — and synthesizing complex sound from simple components was carried out by the German scientist Hermann Helmholtz . By selecting a tuning fork with resonators, G. Helmholtz managed to artificially reproduce various vowels. He investigated the composition of musical sounds, explained the timbre of the sound with a characteristic set of additional tones (harmonics). On the basis of his theory of resonators, G. Helmholtz gave the first physical theory of the ear as a hearing aid. His research laid the foundation for physiological acoustics ^[14] and musical acoustics ^[15] .

The study of bioelectric potentials reveals the ability of individual neurons of the auditory system and their aggregates to process the information contained in acoustic signals (recoding the parameters of sound vibrations into a sequence of nerve impulses, highlighting the characteristic signs of sound recognition, comparing this auditory image with the stored standard, etc.) . Establishing the relationship between the reactions of neurons and the auditory system as a whole is one of the most important tasks of physiological acoustics. Physical analysis of the structure and function of organs of sound emission in humans is important for solving problems of speech synthesis, creating devices for human communication with a machine, and for developing devices for automatic speech recognition.

The study of sound-emitting structures in animals is essential for understanding the acoustic principles of echolocation, orientation, and communication in the animal world. ^[14]

• Biofeedback
• Pitch
• Spectrum
• Timbre
• Formanta
• Stuttering

1. Vartanyan I. А. Physiology of sensory systems: Manual. - SPb. : Lan, 2006. - 224 p. - ISBN 5-8114-0158-2 .
2. Galiev AL On the attenuation of acoustic feedback by the method of transposing the signal spectrum // Sensors, Systems. - 2001. - № 10 . - pp . 51-55 . (inaccessible link)
3. Rabiner L.R. , Shafer R.V. Digital processing of speech signals: Trans. from English / Ed. Nazarov M.V. and Prokhorov Yu.N. - M .: Radio and Communication, 1981. - 496 p.
4. Sapozhkov MA Speech signal in cybernetics and communication. - M .: Svyazyzdat, 1963. - 452 p.
5. Fant G. Acoustic Theory of Speech Formation: Trans. from English / ed. Grigorieva V.S. - M .: Science, 1964. - 284 p.
6. Flanagan J. Analysis, synthesis and speech perception: Per. from English / ed. Pirogov A. A. - M .: Communication, 1968. - 396 p.
7. Chistovich L. A. Ventsov A. V., Granstrem MP and others. Physiology of speech. The perception of speech by man. - L .: Science, 1976. - 388 p.
8. Shannon K. E. Works on information theory and cybernetics: trans. from English / edited by Dobrushina R. L., Lupanova O. B. - M .: Foreign Literature, 1963. - 830 p.
9. Lee BS Effects of Delayed Speech Feedback. // J. Acoust. Soc. Am. , 1950, Iss.6, Vol.22, pp. 824–826.

Research centers

• Speech Correction Center
• SIC Biocibernetics