Question

By decreasing the amplitude of a pure note, its:

• A. speed decreases
• B. wavelength decreases
• C. quality changes
• D. loudness decreases

Answer 1

The correct option is D

loudness decreases

Hint: Knowledge of sound waves

The explanation for the correct option:

D) Loudness decreases

• Loudness refers to the loudness or quietness of the sound heard by the listener.
• Loudness is determined by the strength of the sound wave.
• Intensity is a measure of the amount of energy a sound wave has. The unit of intensity is $decibel\left(dB\right)$.
• Therefore, the strength of the sound wave determines the volume of the noise. Intensity comes from two factors: the amplitude of the sound wave and the distance the sound wave traveled from the sound source.
• Amplitude is a measure of the size of a sound wave. It depends on the amount of energy that caused the wave. Waves with high amplitude have high energy and intensity, so the sound is loud.

The explanation for the incorrect options:

A) Speed decreases

• The speed of sound is defined as the distance traveled by a point of sound waves.
• Compression or decimation covered per unit time.
• The speed of sound remains the same at all frequencies of a particular medium under the same physical conditions.

B) Wavelength decreases

• This is the size of the wave measured from one mountain to the next.
• If you think of a sound wave as a wave of water, the wavelength is simply the distance from the top of the wave to the nearest top.
• Therefore, if the distance between the two peaks is $1m$, the wavelength will be$1m$.

C) Quality changes

• It is used to explain the quality of the waveform displayed to the listener.
• Therefore, the quality of the note depends on the waveform.
• Two sounds of the same pitch and volume played on different instruments do not sound the same because of their different waveforms, different qualities, and timbres.

Therefore, by decreasing the amplitude of a pure note, its loudness decreases (Option D)