Which of the following is proportional to the amplitude of the sound where the frequency remainsconstant?

To determine which quantity is proportional to the amplitude of the sound while the frequency remains constant, we need to understand the relationship between amplitude and other properties of sound.

1. Sound Intensity: Sound intensity is directly proportional to the square of the amplitude of the sound wave. This means that if the amplitude increases, the intensity increases by the square of that change. Mathematically, $I \propto A^2$, where $I$ is the intensity and $A$ is the amplitude.

2. Sound Pressure: Sound pressure is also directly proportional to the amplitude of the sound wave. If the amplitude increases, the sound pressure increases linearly. Mathematically, $P \propto A$, where $P$ is the sound pressure and $A$ is the amplitude.

3. Frequency: The frequency of the sound wave is independent of the amplitude. Therefore, it does not change with changes in amplitude.

Given that the frequency remains constant, the quantities that are proportional to the amplitude of the sound are sound intensity and sound pressure. However, since sound intensity is proportional to the square of the amplitude, the most direct proportional relationship is with sound pressure.

Therefore, the quantity that is proportional to the amplitude of the sound, where the frequency remains constant, is sound pressure.