Path effects

A flute, a guitar, a clarinet, and a piano can each produce a sound at 1 kHz, but the tone quality is different for every instrument. The waveform affects the way a sound is reflected from objects. Acoustics engineers should consider this when designing  sound systems and concert halls. The goal is to make sure that all instruments sound realistic everywhere in the room.

Assume that you have a sound system set up in your living room. You sit on couch and listen to music. Imagine that, for particular placement of speakers with respect to your ears, sounds propagate well at 1, 3, and 5 kHz, but poorly at 2, 4, and 6 kHz. This will affect the way musical instruments sound. It will distort the sounds from some instruments over the sounds from others. Unless all sounds, at all the frequencies, reach your ears in same proportions that come from the speakers, you will not hear the music the way it came from the instruments originally. For some instruments and notes, the sound can be changed so much that it does not resemble the original at all.

Figure given below shows a listener, a speaker, and 3 sound reflectors, also called as baffles. It is certain that the waves traveling along the paths X, Y, and Z will add up to something different, at listener’s ears, than the waves which come directly from the speaker. Path X can be most effective for the bass, path Y most effective for the midrange, and path Z most effective for treble. This will distort waveforms produced by several musical instruments. It is just impossible to design an acoustical room, such as a concert auditorium, to propagate the sound perfectly at all the frequencies for every listener. The best an engineer can do is to optimize the situation and try to avoid existence of any disaster zones.