Our ears detect different sounds by analyzing the properties of pressure waves, such as their frequency, intensity, and complexity. While pitch is primarily determined by the frequency of the sound wave, the perception of different sounds goes beyond just the frequency and involves additional factors.
When sound waves enter our ears, they travel through the ear canal and reach the middle ear. In the middle ear, the sound waves vibrate the eardrum, which in turn transfers the vibrations to three tiny bones called the ossicles: the malleus, incus, and stapes. These bones amplify and transmit the vibrations to the cochlea in the inner ear.
The cochlea is a spiral-shaped, fluid-filled structure lined with hair cells that are responsible for converting sound vibrations into electrical signals. Different regions along the cochlea respond to different frequencies of sound. When a specific region of hair cells is stimulated by vibrations at a particular frequency, they send electrical signals to the brain through the auditory nerve.
While pitch is associated with the frequency of the sound wave, the perception of different sounds also depends on other factors:
Intensity: The intensity or amplitude of a sound wave determines its volume or loudness. Higher intensity waves result in a louder perception.
Complexity: Sounds can be composed of multiple frequencies combined together. The pattern and combination of frequencies determine the complexity of the sound, which contributes to its timbre or quality. Different instruments or voices producing the same pitch will have different timbres due to variations in the combination and strength of overtones.
Harmonics and overtones: Sounds with the same fundamental frequency (pitch) can have different overtones. Overtones are higher-frequency components that give a sound its specific timbre. The presence and distribution of harmonics and overtones influence the perceived quality of a sound.
Therefore, while pressure waves are indeed the physical basis of sound, our perception of different sounds involves a complex interplay of frequency, intensity, complexity, and timbre, as processed and interpreted by our ears and brain.