Acoustics of Brass Instruments

[marzan122]

I pose this question as a concerned researcher. I am currently working on a masters degree in acoustics with research applications on brass instruments.

My main concern is how to direct scientific studies to relevant and applicable topics as judged by musicians and manufacturers. The science of sound propagation in a 3-D waveguide is quite complex. In fact, a theoretical physicist could spend a lot of time and energy playing with equations and still not have much concrete to offer the people that use the instruments day-in and day-out.

So my question....

What do you (as a repairperson, manufacturer, educator, or performer) find interesting about the physics of brass instruments, and what knowledge do you wish science can provide to the music community?

Some topics that are currently under investigation (or could be in the future) include:

1. wall vibrations in brass instruments and their influence on resonant frequencies
2. bore reconstruction: measure the frequency response of an instrument (or part of an instrument, or a mouthpiece) and calculate the internal bore
3. directivity patterns of projected sound and their dependence on played frequency
4. "brassiness": the sound on a brass instruments tends to "break-up" at loud dynamics, but this sound level is different for different notes or different fingering combinations and can thus influence playing conditions

I hope that musicians, manufacturers, and scientists can work together to solve problems encountered in the field. Any thoughts, questions, ideas, would be very interesting to hear.

Thank you,

Matt

[SousaSaver]

You have posed an interesting question here, but be very careful about this can of worms. There is a great deal of hear-say on the internet about the acoustics of brass instruments.

Here is the trouble (in my humble opinion). It is very difficult to talk about this subject scientifically because the process of playing a brass instrument is very subjective and there are variables to isolate; most importantly the player.

I worked a little bit in product development, but not much. I can tell you that everything is a copy of a copy of a copy. All the way from Trumpets to Tubas.

One item to examine that makes a difference in the acoustic properties of brass instruments is the way that the metal is handled. If the metal is too hard or too soft, this effects the way the horn responds. The hardness or softness depends on the way the material is handled and how it is worked.

This is an interesting but difficult question, and I am rambling...

[imperialbari]

There is a German university or trade school in Hannover which has done research in this area, and which offers German makers to have their designs of brass instruments calculated for pitch and intonation. There also has been done research in Vienna on their special trumpet and horn sounds. Maybe take look there to avoid redundant research.

One area I would like to know about is, what happens to the perceived warmth/coldness of sound, when an instrument is optimized to approach intonation of the equal temperament scale?

Klaus

[SousaSaver]

One area I would like to know about is, what happens to the perceived warmth/coldness of sound, when an instrument is optimized to approach intonation of the equal temperament scale?

This is a problem with this discussion. I don't mean to be a pest, but can you please define "warmth/coldness." You might think that this is obvious to everyone, but it isn't.

I also have the same pet peeve with "bright/dark." "Live/dead" makes some sense, but also isn't perfectly clear.

Thanks R.B. - You know who you are...

[imperialbari]

Warmth is about an even representation of overtones, no dives, no peaks in the spectre. Coldness is about an uneven representation of overtones, especially a bad representation of the chord defining partials 3, 5, 7, 9, 11,13,14,15, and so on.

Klaus

[Alex C]

Warmth is about an even representation of overtones, no dives, no peaks in the spectre. Coldness is about an uneven representation of overtones, especially a bad representation of the chord defining partials 3, 5, 7, 9, 11,13,14,15, and so on.

Klaus

Like on clarinets.

[SousaSaver]

Warmth is about an even representation of overtones, no dives, no peaks in the spectre. Coldness is about an uneven representation of overtones, especially a bad representation of the chord defining partials 3, 5, 7, 9, 11,13,14,15, and so on.

Klaus

Klaus -

Where is this information located. I cannot find it. The only reference I can find to "warmth" refers to frequency reverberation:

http://www.owenscorning.com/around/soun ... tml#warmth

http://www.britannica.com/EBchecked/topic/635916/warmth

http://www.traditionalmusic.co.uk/music ... saryUZ.htm

http://www.encyclo.co.uk/define/warmth

http://www.diracdelta.co.uk/science/sou ... ource.html

Thanks in advance -

[imperialbari]

Where is this information located. I cannot find it. The only reference I can find to "warmth" refers to frequency reverberation:

Time is not there to go through your links. However 50+ years with brasses have let me hear very different playing styles based on national schools and on various level of competency.

Without referring to any specific performances I might want to ask you:

When you hear a brass sound with one or more piercing overtones, do you perceive that sound as warm or as cold?

Klaus

[marzan122]

You have posed an interesting question here, but be very careful about this can of worms. There is a great deal of hear-say on the internet about the acoustics of brass instruments.

This is probably the best information you will receive.

Very true. Much of what we think we know about acoustics is a function of our own hearing, which is different from person to person. Hence the "what is warm/dark"-type questions are very difficult. We might both like the same sound but describe it in completely different (even opposite) terms.

Thanks for the input so far.

[marzan122]

This is an interesting but difficult question, and I am rambling...

Ramble on. The more "humble opinions" the better.

Matt

[SousaSaver]

Where is this information located. I cannot find it. The only reference I can find to "warmth" refers to frequency reverberation:

Time is not there to go through your links. However 50+ years with brasses have let me hear very different playing styles based on national schools and on various level of competency.

Without referring to any specific performances I might want to ask you:

When you hear a brass sound with one or more piercing overtones, do you perceive that sound as warm or as cold?

Klaus

The problem is perception. Perception isn't universal, neither is this terminology. Same thing with "Bright/Dark." The answer you receive will depend on who you ask. I appreciate your experience Klaus. I value your opinion and I don't think you are wrong. Maybe it's a matter of semantics.

The real answer is that music performance, especially regarding brasses is subjective. The horn can sound different in your hands than in does to an audience member sitting in the auditorium. Not only does the horn and the player matter but also the room. So many variables...

[imperialbari]

If two persons have the same decibel/frequency hearing curve over an age relevant range then perception shouldn’t be individual. It of course still is, as the said curve is very individual, and hearing is also a result of schooling. Yet I am fairly convinced that if I say a section of amateur trumpet players from a certain country have piercing formants in the area around their 16th partial, then those piercing formant can be measured by the right equipment. And I may be proved wrong an octave or two, as high range octaves are tough to discern.

When I grew up up there were two main Western European schools of oboe playing: the flexible French school with its piercing sound and the warm, but clumsy German school, which caused hypertension with the players. Today the piercing element is gone, as is the clumsiness, at least within the professional area. I happen to know our recently retired oboe professor, who told me, that the French playing style won, but it got rid of its piercing element by a new way of scraping the reeds.

However, the French style was still in a sound sample, when I took a course in sound sculpturing during my college years. Sounds were broken down, among them the oboes tuning A. A diagram showed the energy distribution on the various overtones. The by far loudest single element was E above the staff, that is the octave and a fifth above the nominal note. That E emitted 45% of the total sound energy. The other partials and the root of course each emitted much less energy. The reason, why the human ear still perceived that very pattern of overtones as the tuning A, comes from our brains being engrained with telling the root from Pythagoras’ pattern of overtones no matter how skewed the balance is (OK the balance may become too bad in some cases).

Klaus

[SousaSaver]

If two persons have the same decibel/frequency hearing curve over an age relevant range then perception shouldn’t be individual. It of course still is, as the said curve is very individual, and hearing is also a result of schooling.

Klaus

I think you are misunderstanding me. You defined certain overtones as "warm" and others as "cold." To be perfectly clear, depending on who you ask from person to person, the meaning of "warm" and "cold" changes when referring to how an instrument sounds. It all depends on whom you ask.

Back to acoustics in general. I've been thinking about this today. To really give the topic the proper attention it deserves, you might first want to separate brass instruments into two groups and look at the properties of each; conical and cylindrical.

[Dan Schultz]

There is only one way to find out what different characteristics of brass instruments will do. Build it and blow it. It's called prototyping.... something that does not happen when an instrument is simply copied.

[imperialbari]

Do I write English that badly?

As seen in one of my first postings I stated that warmth is about a balanced overtone spectre, whereas coldness is about uneven representation of the overtones, especially those forming complex chords.

It is allowed to know how different chord constellations sound. It is allowed to consider the overtones of an instrument as an orchestra which is well or badly manned.

Gotta go for now.

Klaus

[DonShirer]

Although acoustics is not my field of physics, if I were looking for research topics I would steer clear of subjective topics like "warmth" or "brassiness". I've always wondered why a really detailed simulation of a brass instrument couldn't accurately predict the pitch of the overtones, so that a designer could better select a configuration which would eliminate the necessity for alternate fingerings. Is it too hard to simulate the passage through the valves and the effect of bends in the tubing?

[Dan Schultz]

.....Is it too hard to simulate the passage through the valves and the effect of bends in the tubing?

I used to think the number of 'crooks' in a tuning circuit or open bugle has one of the determining factors in the performance of multiple brass characteristics. About 15 years ago I worked on an automobile horn project with a World-renowned acoustical engineer/scientist who had worked with the likes of Edison. I asked Mel how crooks affected a wave/air column. His response was "not much".

[marzan122]

...... Is it too hard to simulate the passage through the valves and the effect of bends in the tubing?

Actually, one of the current experts on this is Simon Félix in France. His dissertation was on curved waveguides, and he has published several scientific articles on the subject.

So it is possible to accurately calculate the input impedance of curved waveguides.

If you are not familiar with the term "input impedance"..........

it is defined as the sound pressure divided by the volume velocity of the air at the entrance of the tube (or instrument or waveguide or whatever you like to call it). The input impedance has several peaks that correspond to the frequencies in which energy is delivered to the vibrating system most efficiently. In other words, it gives the natural resonances of the instrument.