Physical explanation of “Breaking Up”

[sirisobhakya]

I have wondered for quite a while about why the sound “breaks up”. Is there any physical explanation? What is the difference in airflow, vibration, or other aspects of the player-horn system?

Is the break-up because of the air is choked at some point (which means the air goes locally supersonic, which is really unlikely!) or from laminar to turbulent at some point? Or is it because the vibration mode of the horn is different so the sound spectrum changes (which is quite likely because heavier bells break up slower)?

Anyone has a theoretical or experimental idea on this subject?

[harrisonreed]

It's just from over blowing the horn, at least that's my experience. It's really easy to over blow a brass 2B. It's really difficult to overblow a sterling 3B. It's really easy to "break up" on a thin, rose brass 88H (often a desirable trait in the horn), it's really difficult to do the same thing on the same horn with the throat of the bell built up or the vibration point there dampened.

The new Alessi horn from Shires is supposedly much thicker in the bell throat, and it's also "consistent throughout the register", ie does not break up.

[Burgerbob]

It's just from over blowing the horn,

But... what does that mean? I think we want to get even more specific. I don't disagree, but I think we can get even more granular.

[Doug Elliott]

I think it is when anything introduces a random or non-harmonic vibration that disturbs the orderly vibration that is the standing wave. It can happen with a thin bell that is not braced enough or in the right place, or outer slide tubing that is thin enough to distort a strong sound wave, and it also happens in the lips if they can't cleanly accept a strong vibration - a double buzz is a form of that, where part of the lip vibrates at a different speed than the main part.

[baileyman]

Do you mean a tone production problem or maybe do you mean the fantastic percussive accent the horn can produce?

[boneagain]

I agree with Doug's answer. I am impressed with the simplicity with which he captures a pretty complex result.

A.H. Benade's "Fundamentals of Musical Acoustics" is not the definitive reference. It is, rather the most accessible I have found that avoid's Wittgenstein's Ladder. Because of Benade's accessibility, I refer to him often. This particular book is available on Kindle, which makes searching for topics like this less tedious.

I searched my hard copy, and even the search was entertaining. I looked up "Distortion" in the Index. The index pointed me to "Heterodyne components; nonlinearity." That, in turn, got me into Chapter 14.2 "Mechanical Origins of Heterodyne Components."

The way I read it, this is related to what happens when one player is out of tune with an adjacent player. The closer the players, the more pronounced the effect. Two trombone players with bells one inch apart and slides a quarter inch or so from "in tune" can produce heterodyning sufficient to rattle back into the chops of both players.

Doug mentions a couple things that can cause this within a single horn. On top of this consider that the sound wave behave more like alternating electric current than direct electric current. The standing wave Doug notes is a result of controlling the alternating within the acoustical behavior of the horn system.

Sharp edges or bends tighter than those in CLOSED wrap systems can cause early reflections that can interfere with the desired vibration patterns. These can vary with the amplitude of the applied signal.

But I recommend NOT being satisfied with the way I read it. I recommend using Benade as a starting point. You can then use the words and concepts found in Benade to search Glasgow, New South Wales, and other great sites for much better explanations.

But I doubt you will find another site that covers the response as nicely as Doug's very first sentence

[harrisonreed]

Do you mean a tone production problem or maybe do you mean the fantastic percussive accent the horn can produce?

That's what I think of "breaking up" as

[imsevimse]

I have wondered for quite a while about why the sound “breaks up”. Is there any physical explanation? What is the difference in airflow, vibration, or other aspects of the player-horn system?

Is the break-up because of the air is choked at some point (which means the air goes locally supersonic, which is really unlikely!) or from laminar to turbulent at some point? Or is it because the vibration mode of the horn is different so the sound spectrum changes (which is quite likely because heavier bells break up slower)?

Anyone has a theoretical or experimental idea on this subject?

This must be an American expression. I have never heard of this or something close to describe a sound. It is not something we say here in my country. When is it used? I have heard "overblow the instrument" here as to negatively describe when you try to put more volume into the instrument than your technique can support. That actually will produce less volume and a thin sound but it will sound like lot of work. A lot of work for very little outcome. Maybe this is the same as "breaking up". I think an instrument can be pushed a lot before it gets nasty if you have the technique To me it has more to do with bad technique than to have a small instrument. Never play louder than you can play beautiful, so to say. The highest overtones must be in balance with the rest of the sound. If not, then it might be "a sound that is breaking up".

/Tom

[Basbasun]

Dougs answer is good.
I have heard a King 2B played with an enormus wolume without what I think is beaking up. Gary Valente. Unbelivily loud and beautiful at that.

[timothy42b]

Dougs answer is good.
I have heard a King 2B played with an enormus wolume without what I think is beaking up. Gary Valente. Unbelivily loud and beautiful at that.

Yes, I heard Wycliffe do that at an ETW concert. Somehow he made the horn not break up, to my ears, where a lesser player would have been distorted into buzz at lower volume. So some of it has to be lip related. I like Doug's answer pointing out both horn and lip possibilities, and Dave's suggestions from Benade.

There is also something called a blat, which I think is a related phenomenon, and I've read somewhere that there can be a shock wave in the air column.