Let's get our hands dirty with JND!
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
(click on the image to watch the movie)
Example #2
(click on the image to watch the movie)
I have created these 2
examples using LMSO and Logic Pro.
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)