Mathew, as a new reader, has asked a lot of questions about the Singers Formant and Formants in general. This has opened a lot of doors that require some explanations. I will try to answer as directly and concisely as possible but this will be a bit long. Since this is a response to his questions you might want to look at his Comments in the Comments section of this blog.
Singing in a contained space such as a bathroom will quite easily produce a tone that matches the resonating space(s) of the room. The room has small enough so that by raising or lowering the pitch of the voice the room resonating space can be discovered. This has nothing to do with the Singers Formant.
However, the fact that you are hearing a high pitch mights indicate that the room is also ‘ringing’ in tune with one of the overtones of your voice. Again, this is not likely to be the Singers Formant.
Choral groups with one singer on a part are able to tune a harmonic chord accurately enough with each other that they will produce a resultant tone. This is sometimes called ringing the chord in Barbershop singing. They can do this because they are not tuning to the tempered scale but to the natural scale wherein the fundamental tone with its well tuned overtones will emphasize other high harmonics. This is not as possible if there is more than one singer on a part unless the singers in each part sing in near perfect unison such that their part will sound like a single voice. A Singers Formant, because it can differ slightly with each singer, would not likely allow such a fine unison to occur and for this reason, few choral directors want their singers to produce Singers Formant.
Formants and overtones are two different things. Overtones are produced by your vocal folds when you sing a well defined fundamental. The overtones are produced by the multiple ways that your vocal folds oscillate. They oscillate longitudinally as a whole, in halfs, in thirds, in fourths etc. and each of these subdivisions produce a weaker tone than the fundamental but they are important because together with the fundamental these overtones give the phonated sound its quality which we call timbre.
The vocal tract, is the space above the vocal folds all the way to the lips of the mouth and this space is divided into the epilaryngeal space, the pharynx and the mouth. Yet this is basically a single long space and it can be adjusted so it will tend to resonate at certain frequencies if a tone from the vocal folds is of about the same frequency. For example, a rather weak third overtone, produced by the vocal folds can be made stronger, that is, louder if it finds a resonance tendency in the vocal tract with the same frequency which will then respond to it. This is similar to what you experienced when you matched the particular resonance of the bathroom and that frequency became louder.
So when we speak of vocal tract formants, we are speaking about the tendency of the vocal tract to resonate certain frequencies. And we can change this ‘tuning’ of the vocal tract in an almost infinite number of ways to allow it to resonate many different frequencies. The two lowest formants, formant one and formant two, have the important task of defining our vowels and, not surprisingly, each vowel has these two formants but each vowel has these formants in different locations in the frequency range.
If you thump the side your larynx with your finger and form the ‘ee’, ‘ay’, ‘ah’, ‘o’, ‘oo’, vowels but without using your voice, you will hear the pitch be lowest for ‘ee’ and highest for ‘ah’ and back down again for ‘oo’. Your thumping on the larynx is inducing the space in the vocal tract to sound its “formant one” for each of these vowels. If you sing these vowels (no thumping, please) your voice will induced the vocal tract to resonate these same frequencies and, in so doing, the vowels become easily identified. If you make a ‘white noise’ with your breath as you do when whispering, but no voiced sound, and again form these vowels without using your voice, you will hear that ‘ee’ is the highest sound and the rest of the vowels will each have lower and lower sounds until you come to the ‘oo’ vowel which is the lowest. In this example your ‘white noise’ breath has a very high frequency and it induces the vocal tract to resonate its “formant two” for each vowel.
So, from this you can deduce that the vowel ‘ee’ has a very low formant one and a very high formant two. And all ‘ee’ vowels have these two formants at the same distance from each other regardless of the singer who is singing them. It is the distance between formant one and formant two that creates the ‘ee’ vowel, not how high or how low these formants are produced. A bass will produce them low but with the same distance between them as a tenor who will produce them much higher but, again with the same distance between them.
Finally the Singers Formant occurs at the frequencies of about 2400 to 3200 Hz. This would place the Singers Formant in the highest octave of the piano, somewhere between C7 (2093.00 HZ) and A7 (3520.00 HZ). Obviously no one can sing a fundamental tone that high but we are talking about overtones of the fundamental which are being emphasized by the special resonance space just above the vocal folds, that is, the aryeppiglotic space.
Formants one and two which produce the distinctive sounds of the vowels (and are usually called Vowel Formants) occur at much lower pitches than does the Singers Formant and, as is mentioned above, produced in the pharynx and mouth through the use of the tongue which separates these two spaces,