Naked Science Forum
General Science => General Science => Topic started by: raghusesha on 25/05/2010 10:24:13
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Hi,
I know that one of the reasons a signal is modulated to a higher frequency is that higher frequency means more energy and hence, can tolerate the noises in channel. I believe the answer for this is in the plank equation (E = h * freq).
But then, why do we see that the bass speaker vibrates more vigorously than the tweeter? Or is that just that the tweeters actually vibrate at a much higher frequency and we cannot see it? Again, if the higher frequencies had more energy, we would need heavier tweeters to stop them from shaking due to the sound itself. But it is quite opposite.
Also, I have noticed that when I plug in my ear phones, I sense the bass more than the high freq sounds. The bass sound kind of "magnifies" in the ear. Is this some kind of resonance?
Regards,
Raghu S
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Hi,
I know that one of the reasons a signal is modulated to a higher frequency is that higher frequency means more energy and hence, can tolerate the noises in channel. I believe the answer for this is in the plank equation (E = h * freq).
But then, why do we see that the bass speaker vibrates more vigorously than the tweeter? Or is that just that the tweeters actually vibrate at a much higher frequency and we cannot see it? Again, if the higher frequencies had more energy, we would need heavier tweeters to stop them from shaking due to the sound itself. But it is quite opposite.
Also, I have noticed that when I plug in my ear phones, I sense the bass more than the high freq sounds. The bass sound kind of "magnifies" in the ear. Is this some kind of resonance?
Regards,
Raghu S
How do you do Raghusesha please be patient with me my spelling may be off and I need to address each statement in segments in order to understand and interpretate correctly.
Set aside Plank's constant for a moment.
Addressing frequency: Bandwidth spectrum scales vary, relative to which portion of it we wish to observe.
You wish to observe speaker momentum "sound"? The audio bandwidth that is the frequencies from about 10 to ~20k Hertz
Plank's constant is used in Quantum physics and is related to light components cell phone signals, radio signals, TV signals and they're at very high to ultra high bandwidth. The trick there is executed to reduce the signal to noise to ratio through of pulse or frequency modulation methods
Not in the realm of audio where it is amplitude modulation..
So for low frequencies in the audio range throw that idea out using Plank's theorums
http://en.wikipedia.org/wiki/Planck_constant
http://en.wikipedia.org/wiki/Signal-to-noise_ratio
Next post I will explain speaker filtering
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You are right that there is more energy at higher frequencies. When you produce sound from a speaker you would like a "flat" response so that there is the same energy/Hz at all frequencies. Therefore, to achieve the same energy at low frequencies the amplitude has to be higher. This is why the speaker movement is much larger.
A speaker has to have a large area and a large cone movement to balance the potential volume the higher frequency midrange and tweeter units can produce. The bass can be improved by using the back of the speaker (corrected for phase) as in folded exponential horn speakers or simple bass reflex speakers but getting to really low frequencies is quite difficult except with very large units. An earphone does not have the same problem because all the energy requirements are so much smaller. It is physically much easier to produce a flat response from an earphone for this reason. The harmonic distortion is also less, because intermodulation products are reduced because of the smaller cone movements.
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Hi,
I know that one of the reasons a signal is modulated to a higher frequency is that higher frequency means more energy and hence, can tolerate the noises in channel. I believe the answer for this is in the plank equation (E = h * freq).
But then, why do we see that the bass speaker vibrates more vigorously than the tweeter? Or is that just that the tweeters actually vibrate at a much higher frequency and we cannot see it? Again, if the higher frequencies had more energy, we would need heavier tweeters to stop them from shaking due to the sound itself. But it is quite opposite.
Also, I have noticed that when I plug in my ear phones, I sense the bass more than the high freq sounds. The bass sound kind of "magnifies" in the ear. Is this some kind of resonance?
Regards,
Raghu S
Hi Again Raghusesha I promised you audio signal filtering. Set the earphones aside they have a small but different characteristics then that of speakers.
In the realm of Audio, it is known to be amplitude dependent at any frequency within its total bandwidth.
We notice when we want that bass to move our body, more then the eardrum, we crank the volume up to a certain magnitude of amplitude, a cheap set of mid-range speakers may suddenly, crack, once this happens, the point of overdriving the speakers has been exceeded. To the trained ear they are considered blown out.
We then go and buy a set that are more expensive.
More expensive? why? Because they now have a tweeter, a mid-range and a bass speaker with crossover filters between the raw audio signal input to each individual speaker.
Crossover circuit is a fancy name for an RLC circuit Resistor Coil and a Capacitor.
Depending on the combination of LC and R (ohm) at a moderate wattage used at mid-range permitting band pass from both sides of the center frequency approxamitly 1000Hz and the combo of just the LC, alone will result in a Reactance which is (dynamic Resistive load or resistance).
There are low band pass and high band pass filters. A combination of the two types adjusted to let the part of the signals high frequecy pass large C value compared to the (L) and part of the low pass Large (L) value compared to (C) at a certain decibel. These are what you call tuned circuts and are used to safe guard the frequency response at the speaker. There is more to it the details can be found on the net.
http://sound.westhost.com/lr-passive.htm
I will soon explain the earphones
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Hi,
I know that one of the reasons a signal is modulated to a higher frequency is that higher frequency means more energy and hence, can tolerate the noises in channel. I believe the answer for this is in the plank equation (E = h * freq).
But then, why do we see that the bass speaker vibrates more vigorously than the tweeter? Or is that just that the tweeters actually vibrate at a much higher frequency and we cannot see it? Again, if the higher frequencies had more energy, we would need heavier tweeters to stop them from shaking due to the sound itself. But it is quite opposite.
Also, I have noticed that when I plug in my ear phones, I sense the bass more than the high freq sounds. The bass sound kind of "magnifies" in the ear. Is this some kind of resonance?
Regards,
Raghu S
Earphones explanation please be patient just getting my ducks in a row
In a nut shell it is frequency response again!
I cheated I am using someone elses words
Piezoelectric earphones also known as crystal earphones are the most sensitive earphones. In fact they are at least 10 times more sensitive than very sensitive magnetic earphones, dynamic earphones, and electrostatic earphones. Sensitive earphones have a very high impedance, which is measured in ohms.
http://catalog.miniscience.com/catalog/electricity/Earphone.html