Let's get our hands dirty with JND!

ear1

This is the third installment (and last, for the time being) of this series of blog entries relative to tuning systems (the previous two were about Pythagorean commas and wolf intervals).

JND stands for Just Noticeable Difference, a concept that can be applied to any kind of measurement. In this case I use it to empirically measure the smallest pitch interval perceivable by the human ear.
I am neither a scientist nor a physiologist so, what I can do is only trying to figure out what is the smallest pitch interval detectable by my ears (and your ears if you are reading this) through some simple experiments.

I stated, on the first of these three articles, that “
JND (is) set at around 5 cents, and can be perceived only under very special circumstances as a slow "beating" between the 2 frequencies, depending on many different factors such as timbre, loudness, register and duration”.

Is that right? Can I prove it or I am simply rehashing concepts expressed by some “authorities”?


Example #1

JNDmovie
(click on the image)

Example #2

JNDmovie
(click on the image)


I have created these 2 examples using LMSO and Logic Pro (screen capture by SnapzPro).

I created a scale with steps of 5
cents each (1/20 of a semitone). Each example starts with a steady bass note, then we hear a second voice starting 100 cents (a tempered semitone) above it and moving down 5 cents at a time until both voices play the same pitch (unison).

On the first example both voices are played by the same “harmonium” sound, on the second one the descending line is played by a “metallophone”.

Do the different timbres of the second example make any difference on the pitch discrimination of the intervals?

When do the 2 sounds stop sounding like 2 different pitches and start sounding like one?

Are these examples too crude to be useful?

JND is an elusive concept. The perception of pitch variations does not depend only on the factors stated above but also on the context (melodic, harmonic) where these variations appear.

Whatever the results of these simple examples it is important to remember that even very small pitch variations, seemingly not relevant and unnoticeable, can make a big difference (as I stated on the first of these three articles).

(I recorded the audio of these 2 short movies as uncompressed 16 bit mono files because any compression would deteriorate the quality of the examples)