PS AUDIO: It’s fundamental

Paul McGowan writes:

I’ll get back to analog output stages soon enough but I got waylaid on our Community Forums area by an article posted by one of our Community Leaders, Gordon.  The article is about how the ear works and, if you’re interested, you can read it here.

I find all this interesting because of a basic fascination I have had with harmonics – the upper frequency components of everything we listen to that define how something sounds.

For example, a piano can be distinguished from a trumpet quite easily despite the fact they may be playing the identical note.  The difference between the audible character of a piano and a trumpet has to do with their overtones or harmonics.  My fascination with these higher level generated tones has to do with the way audio equipment effects them.

I’ll give you a good example.  Yesterday while in the listening room with our Director of Engineering Dave Paananen, we were trying to decide between two types of power supplies on a DAC.  One was a pure linear supply – the other a switch mode power supply – to see which one sounded better on a new DAC we’re working on.  The difference between the two immediately showed itself in the overtones of a singer’s voice – to be specific, the quality and quantity of the reverb within the church setting the singer was in.  With the linear supply it was muddled and unclear – with the SMPS it was clear, evident and rich with overtones.

The point is that nothing changed with what we refer to as the fundamental tone – the starting point for any musical note regardless of how it is generated: voice, piano, guitar pluck – but rather it affected all the generated tones and this fact has always been a point of fascination for me.

One of the interesting points in the article I refer to is that the overtones are so important that one can even remove the fundamental tone and still tell not only what the instrument generating the tone was but what the note was being played!  Think about that for a moment: if we play the note A, which is 440 Hz, the harmonics of it are all higher in frequency than 440Hz – yet we can remove this 440Hz fundamental and immediately know what that frequency was – the brain synthesizing what the fundamental MUST have been to get the harmonics we hear.  Fascinating.

Then, Community Leader Elk added the following comments to the discussion.

“Counter-intuitively, most instruments exhibit stronger harmonics than the fundamental pitch. For example, the second harmonic of a bassoon is twice as loud as the fundamental, with the third harmonic five times as loud.

The flute family exhibits strong fundamental with lower level harmonics. A trumpet has equal fundamental and second harmonic, with slowly dropping levels of higher harmonics.

The human voice is, not surprisingly, highly complex. At lower pitches the fundamental is by far the most prominent. As pitch rises, the second and third increase in intensity and at higher pitches the third dominates.

Another fun quirk of the ear is its ability to predict bass pitches more quickly than they can actually be perceived. A 40Hz low E (lowest note of a bass guitar) has a wave form that takes 1/40th of a second to complete, yet we do not experience any latency in perceiving the tone; we do not need this long to determine the pitch. This is a function of both predictive processing and the ability to perceive pitch through harmonics.”

I may be a total nerd but this stuff really floats my boat.