When you sing, which of the following parameters have a unique value in the sound produced ?

(a) Frequency (b) Wavelength (c) Amplitude (d) Wave Speed

Answer

Singing involves changing musical notes which means changing frequency.

If frequency is not unique, wavelength also cannot be unique.

Loudness also varies while singing. If loudness varies, amplitude cannot be unique.

The speed of sound remains constant and hence unique during the duration of singing.

Hence, (d)