Why do equivalent notes played on different instruments sound different?


So if an A is 440hz, why does a piano playing an A sound different than a violin, a guitar, or someone’s voice making that same A 440 note? It’s obvious that the pitch is the same on each instrument but each instrument has a distinct sound. I’ve never heard an A on a piano and thought, is that a piano or a cello. Why can we distinguish between instruments?

In: 151

Materials and sound reflection mostly.

With different materials u can get “different” sounds. It’s like the: what weights more? 1 pound of feathers or 1 pound of steel?

It’s the same result but the amount of (in this case how the sound moves through the materials and the shape of the item) is different.

Timbre is the word that describes the quality you’re describing. While pitch is the frequency of the note, 440 Hz for A, the shape of the sound wave is not a perfect sine wave. The variation in the shape of the wave will contribute to the quality of the sound.

Anytime you play a note on an instrument, you are actually getting many different overtones of that same note, but higher octaves. So, if you play an A (440 hz), you will also get some sound of the next A (880 hz), and so on. The volume of each of these overtones is specific to the instrument played, so pianos have a specific pattern of volumes that we can recognize.

ETA: Here’s a link with some really good pictures of graphs showing what I’m describing: [link](https://vibrationresearch.com/resources/overtone-comparison-obserview/)

When you play a note on an instrument, the instrument will produce the fundamental frequency, for A, this is 440Hz. But the instrument also produces harmonics. Harmonics are integer multiples of the fundamental frequency. For an A, the 2nd harmonic is 880Hz, 3rd is 1320Hz, etc…

You might also get subharmonics (integer fractions), ie, 220Hz, 110Hz, and maybe even harmonics of the subharmonics, so 660Hz, 1100Hz. Although these usually occur at much much lower amplitudes.

Essentially the relative amplitudes (and phase!) of all of the harmonics together create the specific timber or tonality of the instrument. This is why a violin will sound different from a piano.

Even laboratory sin wave generators cannot produce perfect sin waves, harmonics will always be present, although typically at *very* low amplitude compared to the fundamental.

It’s physics. Sound is developed by a resonance of an object, or system. A violin resonates along its strings and through its wooden form. A piano similarly resonates along its strings and wooden and metal soundboards. The length and tension of the strings affects the sound, as well as the shape and size of the sound board or body of the instrument.

Any sound can be described as a combination (or sum) of many different pitches (or notes), each with different volumes. We can artificially create a note that is A440 with a sine wave that only requires one pitch to describe (a sine wave at 440 Hz), but most tones aren’t that artificially simple. A440 on a violin is actually described by an infinite number of pitches all resonating together (just that the vast majority of those pitches are imperceptible). We hear it as 440Hz because that is the loudest pitch of them all, but also because the next loudest pitches in that tone are all *harmonics* of 440Hz, which means they reinforce the fundamental (generally the lowest pitch in the harmonic content).

There is also an envelope which affects the sound quality of an instrument. The easiest way to think of this is how you make word sounds with your mouth. Just go “oo-ah-oo-ah” out loud. It’s the same fundamental pitch, but the tone changes depending on the shape of your mouth. The shape of your mouth acts like a filter which dampens or augments certain harmonics of the note you are singing. The shape of an instrument has a similar effect.

The timbre, or sound quality of an instrument is created by the unique harmonic content, as well as its envelope and how that envelope interacts with the harmonic content.