Do sound waves have a lower frequency with distance?

Question

I was just studying how sound waves work and how a moving object has higher frequencies when coming towards you, and vice versa. However, if an object is far from you and you and it are stationary, can the air / temperature / density still cause it to sound lower frequency than it really is? Thanks.

Answer 1

You still seem to be a little confused. Frequency does not change during sound wave propagation. What you are thinking of is the Doppler effect, in which a moving SOURCE creates a given frequency sound wave (which has a certain wavelength), which when received by a stationary listenerseems to have a longer or shorter wavelength. This has nothing to do with how far the waves travel. Sound waves of all frequencies (audible) travel at essentially the same speed in air (they are "non-dispersive"). The Doppler effect occurs because the listener and source are in different inertial reference frames. I know that may be a little confusing, but just think of it this way....



You are driving in your car at 668 mph and you emit a sound wave every second (I know the speed is unreasonable, but it makes is easier to understand). This sound wave goes out in front and behind you at 768 mph (speed of sound in air). When you emit the second sound wave (1 second after the first) you are closer to the sound wave in front than the one behind you. This is because you are traveling 100 mph (768mph - 668mph) slower than the front wave, so you aren't too far behind it. While you are traveling at 1436 mph away from the rear sound wave (768mph + 668mph, because you and the sound are going in opposite directions). So now when you emit the second sound wave, the two waves in front will be very close together (147 feet apart) and the ones behind you will be very far apart (2106 feet). Now due this many times and you get a sound wave behind you with a wavelength of 147 feet and one behind you with a wavelength of 2106 feet. When a person standing still behind you and one in front of you hear this, they will not perceive it to be the same 1Hz wave (1 cycle per second) that you sent out.

Answer 2

The only way that would happen would be if there were a strong wind blowing toward or away from you in the direction of the object. Then the frequency would increase or decrease slightly, at least while the wind speed was changing.

Answer 3

YOUR question almost spoke back itself. confident, sound frequencies do variety with distance and propagation. that's named the "Doppler" shift, and is the phenomonon encountered while listening to an drawing near practice from the gap, how the wailing not purely will enhance in quantity yet additionally rises in pitch until the component the practice is nearest, then falls because of the fact the practice strikes removed from you. The frequencies and quantity falling off with distance are almost, yet not somewhat a similar component. same component for police sirens, how they sound deeper in tone with distance, yet piercing while interior of sight. have you ever heard the intense, whistle-like chirping of bats looking prey on a moonless night? I certainly have, yet purely presently found out that we hear the sound an entire 2 seconds after the animal has made it ! (it takes that long for the frequencies to drop in pitch to our listening to variety!)