Viewing a single comment thread. View all comments

Taraxian t1_iy5uz36 wrote

Reply to comment by gooftrupe in Headphone wizardry by SupOrSalad

Frequency IS an increase in sound pressure, it's literally a measure of how fast sound pressure changes back and forth (a vibration)

12

Taraxian t1_iy5w05v wrote

Like, frequency is how fast the magnitude of sound pressure changes, amplitude is how far up it goes before it goes back down, but both those numbers are just derived from one number that's going up and down over time

Failing to understand this is where a lot of audiophile woo sneaks in, like this is why "high-resolution" sound files just means files that can record higher frequency sounds, these two concepts are the same thing

This is the principle behind how a DSD file works and why it has a "bitrate of 1" -- at any given timestamp there's just a 1 or 0 telling you whether the magnitude is currently increasing or decreasing (as opposed to PCM, which directly encodes the 2D image of a waveform we look at, there's a 16 or 32 or 64 bit number telling you what the volume of sound pressure is at any given timestamp)

11

THEOTHERONE9991 t1_iy6fmgt wrote

I don't know what DSD is, but a bitrate of 1 per ear I assume? Otherwise it would have to be mono I suppose. Wait, actually even with that I don't see how a decent result could be produced... I mean maybe. Sorry this is interesting to me, I'd like to know more. This would also require very high samplerates so it can do really weird stepping up and down to reproduce frequency? If it can only go up and down there would be some singular ideal frequency and amplitude (but still subject to samplerate loss) and anything other than that / as it gets farther from it causes more and more loss... also it wouldn't be able produce silence... But I suppose it could produce a very high pitched sound that's above the drivers / human hearing instead. Okay... I want to read more about this now haha, I'm probably overlooking something but I can't imagine how a bitrate of 1 could work.

2

NahbImGood t1_iy87zhy wrote

*bit depth of 1, bitrate of 1 would be 1 bit per channel per second, which wouldn’t sound too good

2

gooftrupe t1_iy5vfyz wrote

Yes of course but the sound pressure + time is two dimensional

1

Taraxian t1_iy5wdfo wrote

Yeah but all our senses include time

4

gooftrupe t1_iy5z296 wrote

Right and therefore those senses are two dimensional

2

13Zero t1_iy6aujl wrote

It’s one dimensional. One input (time) and one output (pressure). When you add stereo, it becomes two dimensional because there are two outputs (right pressure and left pressure).

4

petalmasher t1_iy8shj1 wrote

Frequency and amplitude can be graphed with one line, can't it? http://www.sengpielaudio.com/calculator-wavegraphs.htm

1

gooftrupe t1_iyb3z8m wrote

A one dimensional line would never change direction or osciallate because it has not other dimensions besides length. An x-y plot has 2 dimensions: x and y. Similarly, a sound wave has two dimensions amplitude (sound pressure) and time.

2

petalmasher t1_iyf44ym wrote

Why are you talking about sound in terms of spatial detentions?

1

gooftrupe t1_iyf4hvb wrote

My comments were in reply to a parent comment regarding the ear and hearing, which are spatial

1

gooftrupe t1_iyb16u1 wrote

How is frequency an increase in sound pressure? I can alter frequency while maintaining constant sound pressure, as well as vice versa. Frequency is independent of sound pressure. Again two dimensional

1

gooftrupe t1_iyb3pvk wrote

I think you might be conflating sound pressure (amplitude) and wavelength? Frequency is kind of like the speed of a wave yes, but it's not a product of the sound pressure at all. They're independent. If you haven't heard of sengpiel audio I highly recommend. He explained some of these things pretty well. I use the site for looking up acoustic calculations a lot.

​

http://www.sengpielaudio.com/calculator-wavegraphs.htm

1