Both the frequency and amplitude of a sound wave can be changed as the wave travels through matter. Here are examples of how these changes can occur:
Doppler Effect: The Doppler effect occurs when there is relative motion between the source of the sound and the observer. If the source of sound is moving towards the observer, the frequency of the sound wave appears higher, resulting in a higher pitch. Conversely, if the source is moving away from the observer, the frequency appears lower, resulting in a lower pitch. However, the amplitude of the sound wave is not affected by the Doppler effect.
Reflection and Echoes: When a sound wave encounters a boundary between two media, such as air and a solid surface, it can be reflected. The reflection can cause changes in both the frequency and amplitude of the wave. For example, if a sound wave reflects off a surface that is moving towards the source, the frequency of the reflected wave can be higher, resulting in a higher-pitched echo. Additionally, the amplitude of the reflected wave can be altered depending on the properties of the reflecting surface.
Absorption and Attenuation: As a sound wave travels through a medium, it can experience absorption and attenuation. Absorption refers to the conversion of sound energy into other forms, such as heat, as it interacts with the medium. This absorption can affect both the amplitude and frequency of the wave. Attenuation refers to the reduction in the amplitude of the sound wave as it travels through the medium. Different materials have varying degrees of absorption and attenuation properties, which can modify both the amplitude and frequency of the sound wave.
Scattering: Scattering occurs when sound encounters small particles or irregularities in a medium. It can cause changes in both the frequency and amplitude of the wave. Scattering can lead to phenomena like diffraction and dispersion, which alter the direction and frequency content of the sound wave.
These examples illustrate how both the frequency and amplitude of a sound wave can be modified as it propagates through matter, either due to interactions with the medium or due to relative motion between the source, observer, and reflecting surfaces.