Amplitude, Frequency and Phase

[AudioStudies]

I have a few questions about these topics in relation to recording musical instruments and audio playback. As a simple example, lets start with a piano playing the note middle C and then a few moments later a guitar playing the note middle C. Lets assume both instruments are recorded with the same microphone. It seems to me that middle C determines the frequency, so both instruments would be playing the same frequency. It also seems clear to me that both instruments could play at the same amplitude, if need be for a test. If the same microphone is used, does that necessarily mean they will be recorded with the same phase? Then when playing back a recording of these events, is it possible that both the piano sound and guitar sound could have identical amplitude, frequency and phase? And if that is true, how could one distinguish the piano note from the guitar note? Thanks in advance to all you people out there more knowledgeable than me, who are going to answer this correctly,

 

[mansr]

The difference between instruments manifests (perceptibly) mainly in two distinct aspects: harmonic content and attack/decay. The fundamental frequency may be the same middle C, but the ratio of harmonics differs, as does the amplitude envelope over the duration of a note being played. If the sustain portion of a note is isolated, some instruments can sound surprisingly similar. A recording will of course capture these differences, and on playback we can recognise which instrument was used.

 

[Jimbob54]

I have a few questions about these topics in relation to recording musical instruments and audio playback. As a simple example, lets start with a piano playing the note middle C and then a few moments later a guitar playing the note middle C. Lets assume both instruments are recorded with the same microphone. It seems to me that middle C determines the frequency, so both instruments would be playing the same frequency. It also seems clear to me that both instruments could play at the same amplitude, if need be for a test. If the same microphone is used, does that necessarily mean they will be recorded with the same phase? Then when playing back a recording of these events, is it possible that both the piano sound and guitar sound could have identical amplitude, frequency and phase? And if that is true, how could one distinguish the piano note from the guitar note? Thanks in advance to all you people out there more knowledgeable than me, who are going to answer this correctly,

I think in the first instance you need to have a look at explanations of sound. Particularly as it relates to instrument tone and harmonics. I've seen a few good and fairly easy to understand sessions on YouTube. Even I understood them!

Edit here is one

 

[AudioStudies]

I think in the first instance you need to have a look at explanations of sound. Particularly as it relates to instrument tone and harmonics. I've seen a few good and fairly easy to understand sessions on YouTube. Even I understood them!

Edit here is one

Thanks, I am familiar to a degree with those topics, and I fully understood the answer from Mansr.

 

[Jimbob54]

Thanks, I am familiar to a degree with those topics, and I fully understood the answer from Mansr.

With respect, unless you are being disingenous with your questions, you didn't. And I typed as mansr was answering. Dont ask why a guitar sounds different to a piano playing a note if you already know.

 

[tomtoo]

No they will not be in phase. If you only would know a little about acoustics it would be clear they would not be in phase. To be in Phase the Pianoplayer and the Guitarr Player had to start the tone at the exactly same moment, and had to be at exactly the same distance to the mic.
".. And if that is true, how could one distinguish the piano note from the guitar note? .."
We distinguish a guitar from a piano mostly by it's overtones. And by the way of the attacks.
Dont get me wrong but you mix so much thinks up its hard to get even a point what you like to know?

 

[AudioStudies]

With respect, unless you are being disingenous with your questions, you didn't. And I typed as mansr was answering. Dont ask why a guitar sounds different to a piano playing a note if you already know.

not being disingenuous, just hadn't made the connection between different harmonics, something I learned along time ago existed, and related it back to my thoughts on musical instruments in 2020. I read Mansr before I read yours, and I didn't already know, it just became clear when I read his answer. Please don't assume the worst about me.

 

[Jimbob54]

not being disingenuous, just hadn't made the connection between different harmonics, something I learned along time ago existed, and related it back to my thoughts on musical instruments in 2020. I read Mansr before I read yours, and I didn't already know, it just became clear when I read his answer. Please don't assume the worst about me.

Fair enough

 

[AudioStudies]

To be in Phase the Pianoplayer and the Guitarr Player had to start the tone at the exactly same moment, and had to be at exactly the same distance to the mic.

Ok, lets assume they are the same distance from the mic. My question is related to separate, distinct events, not the piano and guitar playing at the same time. When these subsequent events get recorded by the same microphone at the same distance, is there anything that can be said about phase behavior in audio playback?

 

[Killingbeans]

My question is related to separate, distinct events, not the piano and guitar playing at the same time. When these subsequent events get recorded by the same microphone at the same distance, is there anything that can be said about phase behavior in audio playback?

Things can't be in phase if they don't take place at the same time. That's the whole concept of phase.

 

[AudioStudies]

Things can't be in phase if they don't take place at the same time. That's the whole concept of phase.

Ok, great - thank you. I will take that to mean that nothing can be said about phase angle, etc. of notes that follow one another in audio playback.

 

[tomtoo]

Ok, lets assume they are the same distance from the mic. My question is related to separate, distinct events, not the piano and guitar playing at the same time. When these subsequent events get recorded by the same microphone at the same distance, is there anything that can be said about phase behavior in audio playback?

Dont get you, phase behavior in any musical recording is just not importend. Couse with all the reflections around, its just mixed up.

 

[AudioStudies]

Dont get you, phase behavior in any musical recording is just not importend. Couse with all the reflections around, its just mixed up.

Thanks, I believe you. What then is the purpose of phase inversion switches on some DACs and Preamps - is that related more to things down the chain, like things going on with the speakers?

 

[Killingbeans]

Ok, great - thank you. I will take that to mean that nothing can be said about phase angle, etc. of notes that follow one another in audio playback.

Yes, any signal only has one phase. It doesn't matter if it's a single note or a piece of music.

If you combine two signals, you still only get one phase, while the differences in phase between the original signals gets converted to changes in amplitude and frequency.

 

[Jimbob54]

Ok, great - thank you. I will take that to mean that nothing can be said about phase angle, etc. of notes that follow one another in audio playback.

What is it that you actually want to know? This all stems from comments in your other thread about preamps where Frank said these 3 attributes are all there is to say about preamps.

If you're on a general voyage of discovery about audio reproduction, I'd suggest Wikipedia or other primer sites.

If you have a question about specific equipment, it's behaviour and how to get the best from, ask away.

 

[AudioStudies]

What is it that you actually want to know? This all stems from comments in your other thread about preamps where Frank said these 3 attributes are all there is to say about preamps.

Yes, indeed.

 

[AudioStudies]

If you're on a general voyage of discovery about audio reproduction, I'd suggest Wikipedia or other primer sites.

Certainly willing to check out many sources of info, but my post here has rendered some terrific responses, Mansr for example.

 

[AudioStudies]

If you have a question about specific equipment, it's behaviour and how to get the best from, ask away.

None at the moment, but I may take you up on that later.

 

[AudioStudies]

What is it that you actually want to know?

Everything you know, LOL. I think on the issue of phase of a musical signal though, Killingbeans has fully answered me. I now understand that any recorded signal is all of one phase.

 

[tomtoo]

Thanks, I believe you. What then is the purpose of phase inversion switches on some DACs and Preamps - is that related more to things down the chain, like things going on with the speakers?

Phase makes perfect sense as long as you talk about two sinewaves on your oszilloscope. But it gets much harder if we talk about a speaker in a room.