9 Subjective impressions

Subjective impressions

What does a snapping twig sound like? How about a foghorn?

Chances are, you used everyday words to describe these sounds. Over the millennia, humans had developed a sophisticated vocabulary for describing what we hear. Notions like loudness, pitch and tone quality existed long before scientists could make sophisticated measurements about vibrations. These words reflect subjective impressions formed by our brains- not measurable quantities.

This section defines some of the vocabulary surrounding our human perception of sound.

Loudness

Loudness is our brain’s impression of the “strength” of a sound. Words like “quiet,” “loud,” “silence,” “powerful” describe sounds with different loudness. In everyday language, “volume” (as in “turn up the volume” or “volume knob”) is sometimes used as a synonym for loudness. In this book, I will avoid the word volume (for a variety of reasons).

Pitch

Some sounds don’t have pitch- static from the radio, air rushing out of a tire, or the librarian saying “shhhh”- but most do, especially musical sounds. Pitch is our brain’s impression of the “lowness” or “highness” of a sound. Musicians associate pitch with musical notes- the note “E” is a different pitch than the note “A.” In (Western) musical notation, high notes are located above low notes on the staff. On the piano, low notes are located at the left end of the keyboard. Large musical instruments (like tubas) generally play low pitches and small ones (like the flute) play high pitches.

It’s important to recognize that pitch and loudness are two separate concepts.  It is possible for a low sound to be either quiet or loud. If you are near a foghorn, the sound is extremely loud (but very low pitched). If you are far away, the foghorn sound is quieter, but still has the same low pitch.  It’s also possible for high pitched sounds to be either quiet or loud.

Tone Quality (Timbre)

Timbre (pronounced “tamber”) is the attribute of sound that allows our ears to tell two sounds apart, even when loudness and pitch are the same. Timbre is also called tone quality or tone color.  Every instrument in the orchestra has its own special sound quality. Our ears can tell the sound of a flute from the sound of a guitar- no matter what note it is being played or how loud it is- that’s timbre. Musicians and listeners often use adjectives like warm, dry, pure, nasal, whiny, etc. talking about timbre. Timbre is why different vowel sounds in speech or song- “ee” and “oo”- sound different, even when the pitch and loudness are identical. Timbre is tricky because timbre is defined by what it isn’t– timbre consists of all those characteristics of a (pitched) sound that allow us to distinguish between different sounds that can’t be described by more obvious sonic features (like loudness, pitch and duration).

Duration (perceived)

At first look, duration might seem like an absolute thing, rather than a human perception. However, studies have shown that there are subtle differences between how long we think a sound lasts and how long the vibrations actually last.

Online resources

Watch “What is Tone Color?”^[2] This 4:22 youTube video describes timbre in non-technical way.

Watch “Timbre.” ^[3] This 2:05 youTube video explores the connection between timbre and sound graphs. Different instruments play the same note. A spectrogram, time-domain graph and live FFT of each sound are shown as the sound plays. The video uses Overtone Analyzer by Sygyt Software.

Watch “Pitch and Loudness” ^[4], the 3:00 youTube mentioned in the Stop to Think.