Application of digital inverse filtering techniques to sound field spectral flattening
David T. Talkin, Michael Opauski · The Journal of the Acoustical Society of America · 1977
An acoustic noise field with an essentially flat spectrum from 200 Hz to 5 kHz was needed for a hearing-aid response study. The impulse response of a Brüel and Kjaer hearing-aid test box was determined by driving its speaker with a short-duration pulse and digitizing the output of the reference microphone amplifier. This impulse response was then transformed via an autocorrelation linear predictor analysis into filter coefficients which were used to filter the output of a random number generator. This sequence was desampled and used to drive the test box speaker. The resultant noise field, as measured through the reference microphone, was found to be flat within ±1.5 dB from 80 Hz to 5 kHz. Considerations in the use of this method and its applicability to other sound field spectral flattening situations will be discussed.