if sound pressure = Voltage, then Frequency = Current?

  • Thread starter Thread starter cordura21
  • Start date Start date
cordura21

cordura21

New member
I always find the analogy with Voltage and Volume.
Is current the same as frequency?
And BTW, why is there a difference between the frequency domain and the time domain? Aren't they a micro/macro view of a similar thing?

Cheers, Andrés
 
Current is amperage, the amount of electricity flowing in a wire. Voltage is the force of this current. I know the garden-hose analogy that relates these two; I don't know the analogy that you are speaking of. ("volume is to SPL..." perhaps?)

Frequency is the number of times a sound wave crosses the zero point. A 60Hz sine wave crosses the zero point 60 times per second. I don't think frequency has any relation to current other than an AC current's cycles-per-second rate (which *is* frequency; in the US our AC is at 60Hz, hence the dreaded "60Hz electrical hum"-- it's the "tone" of our power).

I'm also not sure about your domain question, but it could be because time is linear (follows a straight line path) and frequency is logarithmic (ask someone who is good at math about that one).

Did this help? Anyone care to expand upon/correct my answer?
 
Cordura, I'm not sure that your question is really making sense.

Or it could just be me ;)
 
let me see if I can make a better question

when you look at a sound in your computer, you have 2 axis.

The vertical is volume, generally expressed as bits (at least that seems on Protools).
The horizontal is time.
The vertical axis relates to sound pressure, which is volume. When transduced by a mic, that sound pressure is converted into voltage readings, right? Then voltage=volume.
So, is current=frequency? I mean, if you have a higher pitched noise, when it gets converted into electricity: is an electrical signal of more current?
 
cordura21,

Fundamentally, with an X-Y axis of Frequency vs. Amplitude, yes, the amplitude has a direct relationship to the output volume. And yes, the frequency can have a direct relationship to the current (but not really the way you may think, or are theorizing).
(A lot of this explanation involves some linear electronic theory, not the easiest thing to understand if you have no background in electronics - I don't know what your experience is.)

The relationship between voltage and current in an electronic circuit is dependant on the resistance or impedance of that circuit.
A plain resistive load is one that restricts direct current (DC). We're not concerned with this.
An impedance is a measure of inductance, capacitance and resistance that restricts (or allows) an alternating current (AC). Inductance and capacitance in a given AC circuit react differently to different frequencies. Simply put, more current is required to push lower frequencies through an inductive load (say, a speaker), than high frequencies. So, when you're playing your low E bass string through your amp, you are causing more current to flow through your output transistors than if you were to play your guitar (at an identical volume), at the 12th fret.
As I said this is pretty simplistic, and for your purposes (looking at a Freq vs. Amplitude waveform in an audio editor), the amplitude of the waveform is directly proportional to the voltage AND the current flow in your amplifier, and the frequency will also have an effect on the current flow.
This also applies to microphones, but on a smaller scale, as there is much less current flow in the pre-amp circuit than a speaker, and the microphone itself (especially an LDC) is also more capacitive in the way it reacts to sound pressure (but that's another whole medium that others are much more familiar with).

Hope I was clear enough - it's been a while since I've delved into theory. I think I've even confused myself... :confused: :D

mike
 
Power (watts) = Voltage (V) x current (amps)

600watts = 110 x 5.54amps
600watts = 12 x 50amps.

amps relate to power and voltage.

cheers
john
 
Re: let me see if I can make a better question

cordura21 said:
Then voltage=volume.
So, is current=frequency? I mean, if you have a higher pitched noise, when it gets converted into electricity: is an electrical signal of more current?
Click to expand...
No, current is related to voltage by a simple scalar relationship

I=V/R

You could just as easily express a sound wave as current versus time. The waveform would look exactly the same, but the Y axis units would be in Ohms and the scale would change by the factor 1/R where R is the resistance of the particular circuit in question.

Current is not dependent on frequency (Though in music high frequency amplitudes tend to be smaller than low frequent amplitudes). The amount of ENERGY in a sound wave does, however, depend on frequency. High frequency waves have more energy in them than low frequency waves of the same amplitude.

Hope this help,
barefoot
 
teknomike says:
Simply put, more current is required to push lower frequencies through an inductive load (say, a speaker), than high frequencies. So, when you're playing your low E bass string through your amp, you are causing more current to flow through your output transistors than if you were to play your guitar (at an identical volume), at the 12th fret.
Click to expand...

On the other hand, Barefoot says:

The amount of ENERGY in a sound wave does, however, depend on frequency. High frequency waves have more energy in them than low frequency waves of the same amplitude.
Click to expand...

Aren't these two things opposite of each other?

John : I found your post intriguing. Which is an elegant way of saying I didn't understand shit. :-)
 
Andrés,

The energy in a wave is a function of both it's amplitude and it's frequency. Our perception of loudness is actually a response to the amount of ENERGY in a sound wave rather than just simply its amplitude.

Loudness = Energy (very approximately)

Since high frequencies contain more energy at a given amplitude than low frequencies, the amplitude of low frequencies in music is higher than that of high frequencies so that the loudness is approximately even across the spectrum. Make sense?

So teknomike and my statements are not contradictory. Low frequencies have larger amplitudes and therefore higher currents than high frequencies with the same loudness.

barefoot
 
Yes, barefoot is correct, we are not contradicting each other.

Where I am talking specific linear electronic theory (current flow through electronic devices), barefoot is talking about how these theories would apply specifically to the audio realm, and how we perceive the music we hear.

Unfortunately, it does seem like these concepts are at odds with each other. The definition of specific terms can often lead to more confusion.

The basic thing you should get from this is that the frequency scale you see at the bottom of your wave editor does NOT relate DIRECTLY to the current flow in your electronic equipment. The frequency of the signal causes the current flow in the circuitry to change, but it is dependant on the amplitude (voltage) of that specific frequency.

The amplitude (volume/voltage) scale to the right, DOES directly relate to both the voltage and current of the signal through your gear.

I hope I have clarified, rather than confused the issue...:D

Cheers,
mike
 
John was referring to the basic electrical formula for converting Wattage and Amperage. It's handy if you want to know how many amps you will be drawing from a cirucuit using a power amp or lighting system of a specific wattage.

If you ever get into doing large sound and lighting systems on location than that formula becomes vital.

Also known as the WestVirginiA formula for easy remembering.
 
thanks, Texas.
I know the formulae and Ohm's Law, what I didn't understand is what does it have to do with my question. I know those things by heart, like I know that when connecting a mic to a preamp you want maximum voltage transfer, as opposed to maximum power transfer when you are hooking up speaker and amps. That's why you bridge connections in microphones. I know that, but I don't have the slightest clue of WHY is it that way.
Maybe somebody can recommend a good tutorial on electricity and audio.
Cheersm Andre´s
 
"Maybe somebody can recommend a good tutorial on electricity and audio. "

I think they call that a degree in Electrical Engineering ;)
 
You must log in or register to reply here.
Back
Top