### ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

## 1pEA2. Time-frequency display of loudspeakers and electroacoustic impulse
response data using cycle-octave wavelet transforms.

**D. B. (Don) Keele, Jr.
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*DBK Assoc., 536 W. Mishawaka Rd., Elkhart, IN 46517
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A cycle-octave time-frequency display is created by plotting the magnitude
of the wavelet transform, using a Morlet complex Gaussian wavelet, on a
log-frequency scale versus time in number of cycles of the wavelet's center
frequency. This type of display is quite well suited for plotting the decay
response of wideband systems, such as the impulse response of a loudspeaker or
room, because the time scale is long at low frequencies and short at high
frequencies. If the response of typical filters are poltted on this type of
display, the resultant 3-D responses are independent of the filter's center
frequency, i.e., the decay response shape of a particular filter remains the
same as it's center frequency is shifted up and down in log frequency. It can be
shown that the wavelet transform of a system's impulse response is equivalent to
an aggregate of the tone-burst responses of the system evaluated at
equal-percentage-spaced frequencies, where the appropriately scaled and
time-reversed mother wavelet acts as the tone-burst excitation signal.