How Wave Properties Determine Loudness and Pitch
Since sound is a wave, we can relate the properties of sound to the properties of a wave. The amplitude and frequency of a sound wave are key factors in determining how we perceive sound. Specifically, amplitude is closely associated with loudness, while frequency is associated with pitch.
Amplitude and Loudness
The amplitude of a wave determines its loudness. In the case of a sound wave, a higher amplitude corresponds to a louder sound. On the other hand, a lower amplitude corresponds to a quieter or softer sound.
The amplitude of a wave is defined as the maximum displacement or distance moved by a point on a wave from its equilibrium position. In a sound wave, it refers to the maximum pressure change. More energetic vibration corresponds to larger amplitude. The vibration of a source sets the amplitude of a wave through its vibration.
It is important to note that loudness is a subjective quantity that is sensitive to the characteristics of the human ear. The loudness of a sound is also determined by the sensitivity of the ear.
Moreover, amplitude is also related to the energy the wave is carrying. The square of the amplitude determines the intensity or power transferred by the wave per area, which is also proportional to loudness.
For example, sound A with a larger amplitude is louder than sound B, which has a smaller amplitude, meaning a softer sound.
Diagram illustrating the amplitude of a wave.
Frequency and Pitch
The frequency of a sound wave is what your ear understands as pitch. A higher frequency sound has a higher pitch, and a lower frequency sound has a lower pitch.
The human ear can detect a wide range of frequencies. The following table provides information about the lower and upper wavelengths that each species can hear.
| Species | Frequency Range |
|---|---|
| Human | 20 Hz - 20 kHz |
| Dog | 40 Hz - 60 kHz |
| Cat | 55 Hz - 79 kHz |
| Bat | 2 kHz - 110 kHz |
Pitch and loudness of sound.
Demonstrating Amplitude and Frequency
To further understand these concepts, consider the following:
- Compare the sounds made by blowing through vuvuzelas of different sizes.
- You will need to find a few different tuning forks that have different physical characteristics and compare their sounds.
Using an Oscilloscope
The most common oscilloscope controls are for amplitude, frequency, triggering, and channels. The amplitude adjustment of an oscilloscope controls how tall a given voltage will appear on the screen.