Wavelength and speaker

Can I suppose that the wavelength of the sound wave has nothing to do with the speaker itself? it means that the freq of the speaker will cause the wavelength(the distance between comprestions) to be generated in the air?

Can I suppose that the wavelength of the sound wave has nothing to do with the speaker itself? it means that the freq of the speaker will cause the wavelength(the distance between compressions) to be generated in the air?

The speaker distance controls amplitude. The speaker speed controls wavelength.

greg

So, try an experiment in water. It may be easiest to see in a bathtub or a pond, but even in a large bowl of water you should be able to see it easily. Put your hand in the water, or use a small flat plate, and move it back and forth rapidly. Notice that if you move it back and forth a short distance, the waves it produces are small, but they are still there, even though the wavelength is much longer than the distance you move the exciting plate. If you move the plate back and forth at the same rate, but a longer distance, does the wavelength change? Does the amplitude of the waves change? To push the water, do you always have to push a distance equal to the wavelength? Or can you push the water with a very short motion of the "pusher"? Is air significantly different from water in this respect? (Yes, the waves are compression waves, but can you compress air with a motion that's shorter than the wavelength? Even a little bit? Consider a bottle with a rubber diaphragm stretched over the top; if you move the diaphragm even just a little, do you change the air pressure inside the bottle?

Now think about what would happen if you moved the plate back and forth a distance equal to the wavelength. If you moved the plate sinusoidally, would the wave you produced still be sinusoidal?

What if you excited the wave motion with a jet of water? Then the plane of excitation doesn't move at all.

Cheers, Tom

The speaker does not know if it is in air, helium, or under water. Each of these would produce a different wavelength at 100 Hz. At 100 Hz, the speaker cone vibrates back and fourth 100 times a second. How far it moves while it is doing it determines how loud it sounds. I don't have exact numbers, but it is probably safe to bet that the cone moves less than 1 inch. A speaker cone that moved 3 meters would not only drive you out of the house, it would likely run you out of town.

Tam

"Adam"

Wavelength is set by the speed of sound in the medium concerned.

A 100 Hz wave is always 3.4 metres long in ( normal room) air, but much longer ( about 15 metres ) in water.

....... Phil

No, it means the mass that the cone is pushing or pulling (air for example) will travel 3 meters in distance for the time it takes the cone to complete a full cycle of going in, out and back to the starting point.

Since the speed of sound is considered in this example (to keep it simple "769 mph"/"1238 km/h") a constant, lower frequencies take longer for the cone to complete a full cycle, there for, the air mass will move a longer distance before it completes a cycle on the receiving end, your ear for example.

Not sure where you're going with this how ever, I will add to the subject. I am sure you have heard moving trains coming and going by you with it's horn blowing? You'll notice when it's approaching, the sound will be at a higher frequency?

As the horn is alternating to move it's mass of air, colliding with mass movement prior too, will generate a shorter distance of travel for that HZ. You could call this a compressed effect. As it gets closer, the resulting HZ will become closer to being correct. When the train finally goes by, the effects are now stretched and the Hz will appear to go down in frequency.

Of course, the frequency change is limited to the speed of the train.

This is called doppler and is found in many things in nature.

"Jamie the J****ff "

For a stationary observer, Doppler shift depends only on the speed of an approaching or retreating sound source.

....... Phil

Phil, go stick your head under some water. you need it.

And where did I say different you idiot.

I don't know where you got the crazy idea that I was referring to anything but the stationary observer. And even if the observer wasn't stationary. That can also be calculated.

Get off the horse next time before replying, I think you got some horse hairs in your balls. Oh wait, You may not have any balls. Excuse me.

"Jamie the J****ff "

....... Phil

"As it gets closer, the resulting HZ will become closer to being correct."

Your words, not mine.

...... Phil

AH no. Those are you words not mine, sorry.

Phil, don't be such an ignoramus. Don't you have something better to do ?

Or are you trying to get intermit with me again? :)

Ok, Thanks for all advices. Now I know the story...

I have another question in the field. As we know the directivity of a speaker depends upon its wavelength, it means the shorter the wavelength the more directional wave we will have. For a circular opening: Sin ( )=1.2(lambda/distance of the opening) The reason is Diffraction of sound. It means that when the opening of the speaker is larger than the WAVELENGTH of the sound we will have a very small diffraction, but if the opening of the speaker is smaller than the wavelength, the wave would be separated and we will have a high diffraction. The wavelength is the distance between 2 equal points while the separation or diffraction of sound relates to the width of the wave so?

Is there anyone to could direct me to the physical connection of the wavelength and the diffraction please?

thanks

No reply?

Use "diffraction of sound ".

You are now way off topic and becoming a real PITA.

....... Phil

I have searched about it before and I know what is it but I am not able to understand the REAL and physical relationship between diffraction and wavelength . What PITA means?

PITA means Person Involved in Thinking Achievement.

Google is a very difficult tool to master, so don't listen to Phil. He's a real pain in the ass.

Bob

Now go away - TROLL.

..... Phil