Here's why:
* Sound speed is determined by the medium: The speed of sound is primarily dependent on the properties of the medium it travels through (like air, water, or solids). For example, sound travels faster in water than in air.
* Source motion affects frequency and wavelength: What changes when the source moves is the frequency (how many sound waves pass a point per second) and the wavelength (the distance between two peaks of the wave).
The Doppler Effect
This phenomenon is called the Doppler Effect. When a sound source moves towards you:
* Frequency increases: You perceive a higher pitch because more waves are reaching your ear per second.
* Wavelength decreases: The distance between the wave crests gets compressed.
Important Note: While the speed of the sound waves themselves doesn't change, the speed at which the sound waves appear to move towards you *does* change. This is what we perceive as the change in pitch.
