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It seems impossible to find a precise answer to this question. I researched for quite some time, but different sources come up with different definitions, that sometimes disagree or contradict with each other.

So far, I think or understood so far:

LEVEL refers to the loudness or intensity of a signal. It is measured in decibels (dB). Whether peak level or RMS level is used in metering in a DAW or both simultaneously, is something I was not able to find out.

Signal Strength refers to the intensity of a signal as well. Although some sources say that it refers to the amplitude, and others say level refers to amplitude while signal strength refers to intensity. Contradiction it seems.

Amplitude is the displacement of air molecules from their resting position.

Volume is defined as either the perceived loudness of sound OR the level of a signal as it leaves the output.

Is anybody here well versed in audio terminology and can clearly define each term and highlight the differences?

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3 Answers 3

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In Hi-Fi audio circles, Professional audio circles, Amateur audio circles, and other places, these four terms simply do not have definitions that are distinct from each other. In a lot of situations they are used interchangeably, and a difference in meaning between the terms must be understood from context. On top of that, Alex may use the word "Volume" when describing the intensity of a sound he hears, while Barney may use the word "Level" to describe the same thing.

About the only distinction I can point out is that Signal strength will, in the majority of cases, refer to an electronic signal rather than the physical vibrations of air we hear with our ears and call "sound". It's rare to use the word "signal" about sound vibration waves but very common to use it about electrical waves. Aside from that particular distinction, I have read and heard (and said) all four of these terms used to refer to the physical or electronic characteristics that make a sound louder or softer.

(but that ain't all - go ask electric guitarists about the terms "vibrato" and "tremolo"!)

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  • A low volume tremolo sounds great with a low amplitude vibrato. Feb 5 at 3:01
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Not sure if you are looking for a scientific extremely detailed answer but the way I think of them in a practical sense is

Level: numerical value going in or out of a device

Signal strength: general term for whether the input level is adequate/too low/too high to be useful

Amplitude: (don’t know anyone that uses it normally) that means the peak compared to the resting or equilibrium state

Volume: loudness, or usually the output control in the form of a knob, fader, button

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This is what my experience and education tells me.

Amplitude is related to power, it's the actual height of a wave from zero. Any wave (When we're talking waves here, "height" is of the imagined fully rectified wave, so positive and negative phase). They encouraged us to use this term when I was studying for my (BSC Hons) degree in Music Technology in university. So when you're analysing a physical, electronic or digital wave, the amplitude is the measured height of the wave. Sample values are amplitude values (Anybody remember Samplitude? It always reminds me of it). The unit of measurement varies by field. In the digital sound realm, it would usually be dBFS. In electronics, it's probably Volts. So amplitude has a definite meaning, it is not ambiguous at all.

Level is a dynamic peak (Or less common RMS) measurement in an electronic device or system (basically an envelope follower), usually measured with a level meter in order to monitor and satisfy a threshold over time. So I think you can safely define level as a signal's current peak measurement or RMS measurement window. Level is slightly more ambiguous than Amplitude, like you can use it to define the voltage of a particular signal spec, and usually the unit of measurement depends on the system and the context. So for example if it's a digital audio system, the level is displayed in dBFS, if it's analogue, it's... dBV I think (It's been a while). So "level" is less defined in general, but does have well-defined use also. It is not a measurement of loudness or "intensity". But it can affect them.

Signal strength is something I hardly ever use and unless a sound engineer has an electronics background, I don't really think they'd use it. There are times when I can't think of a better term, so it fits well, like in the above description of "level", it may have fitted somewhere. But it might have a definite meaning and unit of measurement in electronics.

Volume - Sound professionals should NEVER use "volume", as it's too ambiguous. It's not a technical term. Volume is the thing you turn up on your TV, HIFI or phone etc. It's a consumer-end term. There is no measurement for volume in the professional sound world. Only on your TV... "I usually have the volume at 38, but I have to turn it down to 33 because the adverts are so damn loud these days!" (Try explaining dynamic range and loudness standards to my dad).

SUMMARY(/TL;DR)
So to summarise, If you're a sound industry professional, Amplitude is well-defined, you should not be using this to mean anything else! Level and Signal strength, one can be used to describe the other so they are quite closely linked and yes, somewhat interchangeable. But volume... If you're using this term in the pro sound industries, then I wouldn't trust your understanding of other basic concepts. If you want to use these terms correctly, and you want to be precisely understood, then volume shouldn't be in your vocabulary. Remove it now! ;)

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