Here are the results of an
investigation on the effect known as "warbling" or "motorboating" that
some makes and models of saxophones have a tendency to produce on low C
and low B natural. Once the sound was recorded and slowed down it
quickly became obvious that my previous hypothesis that the
oscilliations were the result of the note changing from one octave to
the next was in error. There is definitely a pitch change as I suspected but it is neither an octave nor does it go up!
The saxophone
The saxophone used for the demonstration is a Conn C-Melody serial number 61266 that I recently overhauled for a customer. The saxophone was repadded using Music Medic white roo pads with flat metal resonators, and was leak free (of course).
The mouthpiece
Several mouthpieces were tested to find one that generated the clearest warble for this experiment including the very closed tip C melody mouthpiece that originally came with the saxophone. The Brilhart Tonalin tenor mouthpiece that I originally planned to use produced a nice sound, but was next to impossible to make the low notes "warble". An Ernie Northway stock tenor mouthpiece with a Rico Royal 2 1/2 reed was selected for this experiment because it easily produced a distinct "warble" on command. Such a mouthpiece of course would be an unsuitable choice if one's purpose were to perform music rather than to produce a "warble" to investigate its acoustic properties. (see footnote) *
The microphone
The recording was made using a Behringer ECM 8000 omnidirectional condenser measurement microphone with a flat response to 20K Hz. The microphone was placed approximately 12" from the bell of the saxophone.
The recording equipment and software
A Mackie Onyx Satellite firewire recording system patched into a computer using Cool Edit 2000 was used to record the sound tracks for the testing. The Cool Edit 2000 software was also used to slow the recording without changing the pitch.
The recording proceedure
A low C without vibrato was held as a steady long tone playing mezzo forte. The tone was played first as a straight tone and then with the pronounced "warble". I had expected to have to attach a lining material into bell bow or to drop an object into the bell to produce the "straight" tone for the recording, but I was able to turn the "warble" on and off successfully by "voicing" the note differently with the throat and oral cavity. I can't describe what exactly took place "upstream" of the reed's vibration to effect the change, but the effect was sufficient to alter the harmonicity of the produced tone.
The sound analysis software
The sound spectrum was analyzed using the Virtins soundcard multinstrument 2.1 software. A "slice" of the sound recording at both the steady tone and at the point of the "warble" fluctuation in the sound were graphed using the spectrum analyzer portion of the software.
The sounds
Low C Straight Tone
Low C Warble
Low C Warble Slow
The sound spectrum
Note the dramatic change in the second peak when the "warble" pitch change occurs.
No attempt will be made at this time to interpret the results of this demonstration since much more study and research will be required in order to do so. An interesting question has been raised however. That is, if the cause of the warble is the fact that the volume of the bell bow of the saxophone is too large at that portion of the "cone" then why does altering the "voicing" of the note by the player have the effect of counteracting this volume discrepancy?
John Talcott
aka jbtsax
The saxophone
The saxophone used for the demonstration is a Conn C-Melody serial number 61266 that I recently overhauled for a customer. The saxophone was repadded using Music Medic white roo pads with flat metal resonators, and was leak free (of course).
The mouthpiece
Several mouthpieces were tested to find one that generated the clearest warble for this experiment including the very closed tip C melody mouthpiece that originally came with the saxophone. The Brilhart Tonalin tenor mouthpiece that I originally planned to use produced a nice sound, but was next to impossible to make the low notes "warble". An Ernie Northway stock tenor mouthpiece with a Rico Royal 2 1/2 reed was selected for this experiment because it easily produced a distinct "warble" on command. Such a mouthpiece of course would be an unsuitable choice if one's purpose were to perform music rather than to produce a "warble" to investigate its acoustic properties. (see footnote) *
The microphone
The recording was made using a Behringer ECM 8000 omnidirectional condenser measurement microphone with a flat response to 20K Hz. The microphone was placed approximately 12" from the bell of the saxophone.
The recording equipment and software
A Mackie Onyx Satellite firewire recording system patched into a computer using Cool Edit 2000 was used to record the sound tracks for the testing. The Cool Edit 2000 software was also used to slow the recording without changing the pitch.
The recording proceedure
A low C without vibrato was held as a steady long tone playing mezzo forte. The tone was played first as a straight tone and then with the pronounced "warble". I had expected to have to attach a lining material into bell bow or to drop an object into the bell to produce the "straight" tone for the recording, but I was able to turn the "warble" on and off successfully by "voicing" the note differently with the throat and oral cavity. I can't describe what exactly took place "upstream" of the reed's vibration to effect the change, but the effect was sufficient to alter the harmonicity of the produced tone.
The sound analysis software
The sound spectrum was analyzed using the Virtins soundcard multinstrument 2.1 software. A "slice" of the sound recording at both the steady tone and at the point of the "warble" fluctuation in the sound were graphed using the spectrum analyzer portion of the software.
The sounds
Low C Straight Tone
Low C Warble
Low C Warble Slow
The sound spectrum
Note the dramatic change in the second peak when the "warble" pitch change occurs.
No attempt will be made at this time to interpret the results of this demonstration since much more study and research will be required in order to do so. An interesting question has been raised however. That is, if the cause of the warble is the fact that the volume of the bell bow of the saxophone is too large at that portion of the "cone" then why does altering the "voicing" of the note by the player have the effect of counteracting this volume discrepancy?
John Talcott
aka jbtsax