One for the physicists

Proteus · Posted: Sun Nov 19, 2023 7:44 pm Post subject: One for the physicists

To be clear: I'm not a physicist...and I'm not trying to start a wildfire here. That said, I would like to know in layman physics terms how the parameters of mouthpiece sizes (ie. cup volume, depth, etc.) influence the resulting timbral colour and volume of sound.

All I've understood from various discussions here is that 'energy in' excites various standing waves to various degrees...if that's even close to being correct(??). But wouldn't any mouthpiece do that? Is it that the parameters of the mouthpiece directly influence the resulting characteristics of the output waveforms...and therefore the resulting timbral (overtone) spectrum?

If this is more-or-less the case, then the horn is in large part more or less an amplifier? (I'm thinking power amp in hifi terms here). And the mouthpiece is more like the preamp? (with built-in 'tone controls').

Any physicists or acousticians out there?
Thx.
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etc-etc · Heavyweight Member Joined: 19 Jan 2008 Posts: 6103

Vibrations of lip aperture will include more overtones if the motion is non-sinusoidal/non-harmonic (e.g., approaching a square-shaped wave). This can be helped by reducing the depth of the mouthpiece. In the extreme case, lips will bounce away from the shallow mouthpiece surface, and the sound, rich with overtones will be very bright ("lead mouthpiece").

In contrast, a deep mouthpiece will facilitate a sinusoidal/harmonic vibration, making the sound dark (typical for flugelhorn or brass band cornet setup).

JayKosta · Posted: Mon Nov 20, 2023 6:10 am Post subject:

This is my layman's view -

Trumpet does not function as an amplifier - it 'concentrates' (not like an electric condenser) and 'refines' the air pressure vibrations to produce its sound.

Mouthpiece rim shape and inner / outer diameter affect how the rim interfaces with the players lips, and can affect how the player is able to adjust their lips. And lip positioning affects how the vibration / pulsation is produced.

The size and shape of the cup / throat / backbore affect how the vibrations get reflected and 'bounced around'. The amount of interior space acts somewhat like an automobile shock absorber of the interior pressure and how that pressure affects the lips.
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kalijah · Posted: Mon Nov 20, 2023 8:06 am Post subject:

Ronnman · Posted: Mon Nov 20, 2023 8:09 am Post subject:

See the below link to a paper Matt Frost wrote. It’s long at 383 pages, but look through the contents and you will likely locate some information you seek.
Ron

https://digital.lib.washington.edu/researchworks/bitstream/handle/1773/25455/Frost_washington_0250E_12622.pdf?sequence=1&isAllowed=y
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lipshurt · Posted: Mon Nov 20, 2023 9:15 am Post subject:

I usually like what Kalifa brings to the conversation, but this one:

“ The instrument is a resonator, not an amplifier of any sort”

Seems to be a good example of something the layman can take issue with, and maybe lead to developing a bad attitude about science in general.

If you buzz a mouthpiece and then while buzzing insert that buzz into a trumpet, it gets way louder. Therefore it has to be an amplifier of SOME sort. perhaps all it does is resonate, but if its louder, it’s an amplifier of some sort.

I am defining ‘amplifier” as something that makes sound louder.
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kehaulani · Posted: Mon Nov 20, 2023 9:46 am Post subject:

"Would it help?"

Rudolf Abel's character in "Bridge of Lies".

Just curious, why do you want to know? Are you going to start working on mouthpieces?
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kalijah · Posted: Mon Nov 20, 2023 9:52 am Post subject:

Proteus · Posted: Mon Nov 20, 2023 11:33 am Post subject:

Steve A · Posted: Mon Nov 20, 2023 12:27 pm Post subject:

kalijah · Posted: Mon Nov 20, 2023 1:16 pm Post subject:

Another distinction is that an amplifier would ideally have a "flat" frequency response. Showing no favoritism of amplified frequency. Obviously not a quality of the instrument.

The resonator, in this case the trumpet has very distinct, defined and STRONG resonances. A quality that would be a nightmare for an actual sound power amplifier but is essential to the trumpet or any brass instrument.

Billy B · Posted: Mon Nov 20, 2023 2:57 pm Post subject:

William Adam did a behind the screen session where he played excerpts ranging from Brahms to Brandenburg to Beethoven. Everyone was gassed at how great he sounded on all of the excerpts. He played them all on a Bb trumpet and one mouthpiece. Draw your own conclusions.
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Tpt_Guy · Posted: Mon Nov 20, 2023 3:46 pm Post subject: Re: One for the physicists

lipshurt · Posted: Sun Nov 26, 2023 10:08 am Post subject:

“The trumpet is a resonator, not an amplifier of ANY SORT”

Come on, the trumpet makes the mouthpiece louder. If it’s louder, it’s been amplified. It’s crazy to say that it has not been amplified. It’s an amplifier of SOME SORT.

How hard is that to wrap your head around?

Resonator:

“ A resonator is a device or system that exhibits resonance or resonant behavior. That is, it naturally oscillates with greater amplitude at some frequencies, called resonant frequencies”

Greater AMPLITUDE
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JayKosta · Posted: Sun Nov 26, 2023 10:26 am Post subject:

Steve A · Posted: Sun Nov 26, 2023 2:11 pm Post subject: