Answer:
The observer hears a loud sound
Explanation:
In order to know if the observer hears a loud or a quiet sound, you need to know if there is a constructive or destructive interference between the sound waves of the loudspeakers.
You first calculate the distance between the observer and the loudspeakers.
The distances are given by:
d1: distance to loudspeaker A = 2.10m
d2: distance to loudspeaker B
Next, you calculate the wavelength of the sound waves by using the following formula:
vs: speed of sound = 343 m/s
f: frequency of the waves = 400Hz
λ: wavelength
Next, you calculate the path difference between the distance from the observer to the loudspeakers:
You obtain a constructive interference (loud sound) if the quotient between the wavelength of the sound and the difference path is an integer:
Then, there will be a constructive interference, and the sound who the observer hears is loud.