Both the frequency and amplitude of a sound wave can be changed when it travels through matter. Here are examples of how these properties can be altered:
Frequency Changes:
- Doppler Effect: When a sound source or the listener is in motion relative to each other, the frequency of the sound wave appears to change. If the source or listener is moving towards each other, the frequency is perceived as higher (higher pitch). Conversely, if they are moving away from each other, the frequency is perceived as lower (lower pitch). This effect is commonly experienced with moving vehicles and sirens.
- Frequency Modulation (FM): In FM radio broadcasting, the frequency of the carrier wave is modulated by the audio signal. This modulation allows for the transmission of varying frequencies, resulting in the reproduction of different pitches or tones.
Amplitude Changes:
- Sound Intensity: The amplitude of a sound wave determines its intensity or loudness. Increasing the amplitude of a sound wave results in a louder sound, while decreasing the amplitude leads to a softer sound. This change in amplitude can be achieved by adjusting the energy or power of the sound source.
- Sound Attenuation: As sound waves travel through a medium, they can experience attenuation, which is a decrease in amplitude due to factors such as absorption, scattering, or geometric spreading. For example, sound traveling through air tends to attenuate over distance, resulting in a decrease in amplitude as it propagates further away from the source.
It's important to note that changes in frequency and amplitude are distinct and can occur independently. These examples demonstrate how each property can be altered individually, but in reality, various factors can affect both frequency and amplitude simultaneously as sound waves propagate through different media.