Final answer:
Beat frequency is calculated by subtracting one frequency from another; the car horns emit a beat frequency of 0.7 Hz, while the piano strings result in beat frequencies of 0.3 Hz, 0.2 Hz, and 0.5 Hz for the respective pairs of strings.
Step-by-step explanation:
The concept being asked about relates to beat frequency, which is a phenomena occurring when two sound waves of slightly different frequencies are played together, resulting in a fluctuating sound wave that has the frequency of the difference between the two original sound waves. In the case of the custom-built car horns with frequencies of 263.8 Hz and 264.5 Hz, the beat frequency can be determined by subtracting one frequency from the other, which would result in a beat frequency of 0.7 Hz.
For different musical notes played together, the beat frequencies are: (a) between A (220 Hz) and C (264 Hz) the beat frequency is 44 Hz, (b) between D (297 Hz) and F (352 Hz) the beat frequency is 55 Hz, and (c) when all four notes are played together, various beat frequencies can result due to interactions between each pair of notes.
When a piano hammer hits three strings that emit frequencies of 127.8, 128.1, and 128.3 Hz, the beat frequencies that result will be the differences between the pairs of strings, specifically: 0.3 Hz between the first and second string, 0.2 Hz between the second and third string, and 0.5 Hz between the first and third string.