Page 133 - Master Handbook of Acoustics

filter, sometimes called a transversal filter. Digital samples are input to the filter and applied to the
−1
top section of z blocks comprising a tapped delay line; the middle section shows multiplication by
filter coefficients; these outputs are summed to produce the filter’s output samples. In this way, the

signal’s frequency response can be altered.

FIGURE 5-26 A finite impulse response (FIR) filter showing delay, multiplication, and summing to

implement signal filtering.

Digital filters are part of a larger technology known as digital signal processing (DSP). DSP is
widely used throughout the audio industry in many different applications ranging from processing of
music signals for playback to signal analysis of room acoustics. For example, DSP can be applied to
loudspeaker-room-listener problems. A microphone placed at the listening position measures the
frequency and phase response of a loudspeaker’s output in a listening room, and from that data,
inverse equalization is created to compensate for defects caused by the loudspeaker and the room
acoustics.