Answer:
It could be a stringed instrument or an open pipe.
Step-by-step explanation:
Let v be the speed of sound, y be wavelength and f be frequency.
v = yf
f= v/y; v is constant.
In a stringed instrument, the fundamental frequency note is heard when the length of the string, l = y/2; y= 2l
f′= v/2l
The second harmonic is heard when l= y
f"= v/y
...
f'''= 3v/2l
We can infer that f"= 2f'
f'''= 3f'
This is similar to the values in the question as;
523.26 =2(261.63) and so on.
Same thing happens with open pipes.