Respuesta :
It's called ' interference '.
If the strings are 'in tune' (same frequency) and in phase, then
they overlap to make a louder sound ... CONstructive interference.
If the strings are 'in tune' (same frequency) but out of phase, then
they overlap to make a softer sound ... DEstructive interference.
If the strings are 'out of tune' (different frequencies), then they overlap
to make a sound that's louder at some times and softer at other times.
The louder and softer pattern creates a new sound, called the 'beat'.
Its frequency is the difference in the frequencies of the two strings.
If the strings are 'in tune' (same frequency) and in phase, then
they overlap to make a louder sound ... CONstructive interference.
If the strings are 'in tune' (same frequency) but out of phase, then
they overlap to make a softer sound ... DEstructive interference.
If the strings are 'out of tune' (different frequencies), then they overlap
to make a sound that's louder at some times and softer at other times.
The louder and softer pattern creates a new sound, called the 'beat'.
Its frequency is the difference in the frequencies of the two strings.