Someone please explain exactly what frequency is to me

[Winding Road]

I've picked up a couple of digital recording books and I've gotten lost at times at what exactly frequency means.

I think that I have a good understanding of what exactly the definitions that are given are, but I want to reafirm it.

Please explain how it relates to amplitude and how waves go through a cycle of positive and negative amplitude.

Explanations in as simple a way as possible. And, include analogies please.

 

[RAK]

I've picked up a couple of digital recording books and I've gotten lost at times at what exactly frequency means.

I think that I have a good understanding of what exactly the definitions that are given are, but I want to reafirm it.

Please explain how it relates to amplitude and how waves go through a cycle of positive and negative amplitude.

Explanations in as simple a way as possible. And, include analogies please.

This is the simplest way to explain it.

volume(percieved)=amplitude(scientific measurement)
pitch(percieved)=frequency(scientific measurement)

It's difficult to explain in even a simple way without looking at a sine wave on a oscilloscope. However, on a scope, the Y axis shows amplitude, measured in volts, and the X axix shows the period (time).

The amplitude voltage relates to volume in this way 20logVout/Vin=dB(SPL)
Sorry to get technical there.

Now, imagine a sine wave, the time from peak to peak (or trough to trough) is called the period. Frequency is the inverse of the period of the wave (1/Period). So you would measure the amount of time between peaks on the scope, and take the inverse, and you would get the frequency. In the musical world, we assign these frequencies to a certain "pitch" so for example 440 herz (herz=cycles/second) we call an A.

Also, since you mentioned you were reading digital recording books, in the A/D/A process, amplitude relates to bit depth, and frequency relates to sample rate.

 

[Winding Road]

Thanks. That sheds more light on the issue to me.

I've perceived frequency as the number of vibrations of sound particles that occur between a positive and negative peak of a specific number of wave particles. Is this a correct assesment?

Like, say you take a limited group of sound particles and you take the highest and lowest amplitude in that group. The frequency is then the number of vibrartions from highest to lowest?

My whole problem has been trying to vision the movement of sound waves.
Though I've studied some trigonometry, I've never gone in depth on sine waves that's why it's been hard for me to understand the concept of waves graphed in one.

 

[XLR]

Look at the strings of a guitar. Play a variety of pitches spanning the range of the instrument. Play each pitch both loudly and softly. Use a magnifying lense or videotape in extreme closeup, then play back in slow motion. What you'll see is:

Frequency simply means how fast the vibrations occur after each string pluck. The higher the pitch, the faster the vibrations. Amplitude means how far back and forth the string moves. Louder sounds have more energy and the string moves farther back and forth.

Tim

 

[RAK]

Thanks. That sheds more light on the issue to me.

I've perceived frequency as the number of vibrations of sound particles that occur between a positive and negative peak of a specific number of wave particles. Is this a correct assesment?

Like, say you take a limited group of sound particles and you take the highest and lowest amplitude in that group. The frequency is then the number of vibrartions from highest to lowest?

My whole problem has been trying to vision the movement of sound waves.
Though I've studied some trigonometry, I've never gone in depth on sine waves that's why it's been hard for me to understand the concept of waves graphed in one.

You're mixing up amplitude and frequency. With frequency, ignore the Y-Axis.
Frequency only has to do with time, which is along the X-Axis.
So again picture a sine wave. If you measure the time from one peak to the other, this is the Period, or the time it takes to make one cycle. If you then take the inverse of this Period, that is the frequency, which is measured in Hz (cycles/second).

Just pulling a number out of my head, say you look at your sine wave and you measure the period (peak to peak) to be 20 ms. You would then create the equation of 1/.02 seconds = 50 Hz. So the frequency of that wave is 50 Hz. And remember Hz = cycles per second. So this wave makes 50 cycles/second. In musical terms we would label this 50 Hz wave with a pitch (this should roughly be around a very low A).

 

[Winding Road]

Ok, thanks a lot guys for clearing up and affirming some of what I felt. That's why I posted this on here. I haven't had any help from anyone besides reading the books which don't offer many explanations or analogies for their terms.

 

[XLR]

If you want to get into the subject in detail, The Psychology of Music by Carl E. Seashore is a good read. He talks about music's basic elements of frequency, intensity (amplitide), duration and timbre.

Frequency and amplitude are, of course, a matter of physics but in the musical sense it's our perception of them that's what matters. Anyway, it's a good book.

Tim