I am teaching a basic overview of what audio frequency is and how it relates to pitch, timbre, and perceived loudness.

1. Frequency
Sasha Vulovic

2. Introduction
• My name is Sasha, I live in Detroit, Michigan.
I’m from Seattle, lived in Tucson for a couple
years and moved to Detroit a year and a half
ago.
• I’m not super familiar with music recording or
any recording devices. I do play music.
• I will be teaching a basic overview of
frequency.
• Thanks!

3. What Frequency Is
• Frequency refers to the number of sound waves per
second: measured in Hertz, number of cycles per
second
• Sound will travel at the same speed always, 340 meters
per second or about 1/ 5 of a mile. But within that
direction of sound there is the oscillation of each
soundwave
• - like ocean waves, one cycle would be measured from
wave peak to wave peak- but unlike ocean waves,
sound waves oscillate IN the direction they are moving.

4. Not Identical to Pitch!
• Just as amplitude can be said to be the
quantitative measure that affects our
perception of loudness, so frequency is the
quantitative measure that affects our
perception of pitch.
• Amplitude is not loudness, frequency is not
pitch, but they affect those audio perceptions.

5. Our Hearing Range
• Our hearing range extends from a low
frequency of 20 Hertz (20 soundwaves per
second) to a high frequency of 20,000 Hertz.
As adults due to worsened hearing over time
and exposure to noise, the highest frequency
we can hear is more often 18,000 to 19,000
hertz.
• The higher the frequency, the higher the
pitch we perceive it to be.

6. Notes emit more than one frequency..
Recognize the fundamental
• What is interesting is that despite our being able to name
the pitch of a sound- say middle C- it is very rare that the
frequency corresponding to the middle C pitch is the only
one emitted in the sound. Most instruments, voices, and
objects that create sounds we perceive to be of one
pitch, are actually emitting several frequencies.
• A tuner, on the other hand, will have less variation in its
frequency and emit simply the fundamental frequency: we
call its waveform sinusoidal
• .The frequency that corresponds to the pitch we recognize
is usually the lowest one emitted, and it is called the
fundamental frequency.

7. Harmonic Overtones
• Often the multiple higher frequencies are in harmony with
this fundamental; they'll be multiples of the fundamental
frequency.
• So say the fundamental frequency of a note played at
middle C is 130 Hertz; other frequencies emitted could be
260 Hertz, 390 Hertz, 520 Hertz (all multiples of 130 Hertz).
• Every time you double the frequency of a sound or note,
the corresponding pitch is an octave higher.
• So while there will be some frequencies of higher pitched
C's playing while the fundamental frequency is middle C,
the note and pitch will still sound clean and on-key because
the pitches are in harmony. Thus these overtone
frequencies are called harmonics.

8. Inharmonic Overtones
• It's not always the case that these overtone
frequencies are multiples of the fundamental. So
when it's the case that you have higher
frequencies than the fundamental being emitted
that are not exact multiples, these will be “off-
key” and are called inharmonic frequencies.
• The overtone frequencies (higher than the
fundamental) plus the fundamental frequency
together are called partial frequencies or partials.

9. Timbre
• Timbre is a tonal quality affected by the presence of multiple
frequencies.
• A tuner playing middle C sounds very different from an opera singer
singing the note or a piano or a banjo
• even the same note sung by the same person can emit different
variations of frequencies, and thus contain different timbres,
depending on the shape of the singer's mouth as breath is pushed
out.
• An interesting experiment related to this was watching the visual
representations of audio frequency vary as our teacher sang
different vowels all at the same frequency:
• I and O emit higher overtone frequencies than A or E though we
would all recognize the fundamental frequency and thus pitch as
being the same throughout. It's an interesting phenomenon to keep
in mind for music or even speech- how different words, people's
names, sung or spoken affect the tonal qualities our listeners
perceive..

10. Frequency affecting Perceived
Loudness
• Though we hear well enough the overtone frequencies
to differentiate between the tones of different
instruments or tuners playing the same note, we don't
hear very high- or very low- frequencies as WELL.
• Our range of hearing does stop at about 20 Hertz in the
low range and 20,000 Hertz in the high range but it
does not stop abruptly; frequencies of 15,000 Hertz we
would have more difficulty hearing than frequencies of
300 Hertz.
• Thus, though frequency does not affect amplitude, it
does affect our perceived loudness.

11. Equal Loudness Contour Curves
• A frequency of 16,000 Hertz played at the same amplitude as a frequency
of 300 Hertz, will sound less loud
• Equal loudness contours are the visual graph describing this phenomenon.
• Listeners were asked to adjust the volume of notes corresponding to a
large range of frequencies so that the sounds they heard would be
"equally loud." The earliest researchers to make a big project of this were
Fletcher and Munson and thus these curves are often named after them
but their experiments were less accurate than later ones.
• What researchers did find was:
• 1. To keep the level of perceived loudness the same across different
frequencies, the amplitude of higher and lower frequencies needed to be
greater and greater, than the lower amplitudes of frequencies right in the
middle of our hearing range
• 2. Each person had their own variations even within that general pattern.
The frequency corresponding to a pitch of F# might sound a lot louder to
me, played at the same amplitude as G, than it would to you, as an
example.