Converting Propagation Distance to Delay Length

• We may regard the delay-line memory itself as the fixed ``air'' that propagates sound samples at a fixed speed $c$.

• The number of delay samples is the propagation distance divided by the distance sound propagates in one sample.

• If the listening point is $d$ meters away from the source, then the delay line length $M$ needs to be
  $$M = \frac{d}{X}= \frac{d}{cT}$$    samples$$.$$