Question

For each of the following pairs of frequencies, specify whether you should expect to hear when they are played simultaneously: beats, or a difference tone, or neither, or both together. Use B, D, N, or T respectively, so that your answer might look like BDTND. The pairs are 4205 Hz and 4232 Hz

4160 Hz and 4176 Hz

3650 Hz and 3675 Hz 1

875 Hz and 1882 Hz

4550 Hz and 4556 Hz

Answer 1

First find the beat frequencies in all the cases.

Pair 1 - 4205 Hz and 4232 Hz. Beat Frequency = 27Hz - T

Pair 2 - 4160 Hz and 4176 Hz. Beat Frequency = 16Hz - T

Pair 3 - 3650 Hz and 3675 Hz. Beat Frequency = 25Hz - T

Pair 4 - 1875 Hz and 1882 Hz. Beat Frequency = 7Hz - B

Pair 5 - 4550 Hz and 4556 Hz. Beat Frequency = 6Hz - B

For cases when beat frequency is less than about 10 Hz two waves are very close in frequency and you will hear only one pitch. So beats will be heared.

For cases when beat frequency is in the range of 10-60 Hz, we hear both the beats and difference tone together because it is tough for the brain to interpret properly.

When beat frequency is greater than 60Hz we hear a difference tone.