Abosolute Pitch: Differentiating between B, C and C# in pure pitch recall

I've hit a snag in my absolute pitch recall from memory. Now sometimes when I attempt to sing middle C out of the blue with no external reference, I sing a B note instead.  Once in a while I also sing a C#. Interestingly, I'm always more or less on one of the three notes. I don't sing in between them. That's hopeful!

But how do I learn to recognizing the difference between those notes?

What am I trying to do really? I am trying to have memory recall of three different vibrations per second: 246.942,  261.626, and 277.183.

Current method: random quizzes of those three notes during the day to see if I can learn to recognize the difference. Here is a keyboard to use in hearing the difference.

When comparing the notes side by side, it is easy for most people to tell which is higher and which is lower. But what about pitch recall?

More research:

• In Western music, we an adjusted "tempered" scale. Because of that, the difference is slightly less from a B note to a C note (14.684) than a C note to a C# (15.557).


• one equal tempered semitone is equal to 100 cents, and so an octave is 1200 cents.


• Each auditory nerve cell is a little oscillator, tuned to respond to vibrations in a narrow frequency band corresponding to the nerve’s position on the Basilar Membrane.


• Basilar Membrane contains 30,000 hair/nerve cells along 35 mm length


• Each octave is an equal shift of about 3.5 mm


• Each pure tone is localized to a Critical Band of about 1.2 mm.


• Each pure tone excites about 1300 hair cells covering a 15% frequency range (< minor third).


• brain can  resolve position and width of pure tone distribution to 1/20 of full width = 0.06 mm = frequency ratio 1.01 or about 29 cents.


• The 'just noticeable' difference [between two pitches] is often defined as 5 cents - NIST


• James Taylor says using a capo on a guitar can make it sharp by much as 6 to 8 cents


• There are roughly 20 little tiny steps between a B and C note where you could hear some difference.


• The human ear can hear sounds between 15 and 20,000 vibrations per second.


• Human voices can make sounds in the range of 100 Hz to 5,000 Hz. (The record for low is held by Tim Storms who can sing lower than humans can hear at 8 Hz.)


• An 88 key piano runs from A0 at 27.5 vibrations per second, up to C8 at 4,186.01 vibrations per second.

Here is a chart of musical note frequencies, including the correct frequency for every key on an 88 key piano:

Frequencies of the equal temperament
C / B#	16.352	32.703	65.406	130.813	261.626	523.251	1046.502	2093.005	4186.009	8372.018	16744.036
C# / Db	17.324	34.648	69.296	138.591	277.183	554.365	1108.731	2217.461	4434.922	8869.844	17739.688
D	18.354	36.708	73.416	146.832	293.665	587.330	1174.659	2349.318	4698.636	9397.273	18794.545
D# / Eb	19.445	38.891	77.782	155.563	311.127	622.254	1244.508	2489.016	4978.032	9956.063	19912.127
E / Fb	20.602	41.203	82.407	164.814	329.628	659.255	1318.510	2637.020	5274.041	10548.082	-
F / E#	21.827	43.654	87.307	174.614	349.228	698.456	1396.913	2793.826	5587.652	11175.303	-
F# / Gb	23.125	46.249	92.499	184.997	369.994	739.989	1479.978	2959.955	5919.911	11839.822	-
G	24.500	48.999	97.999	195.998	391.995	783.991	1567.982	3135.963	6271.927	12543.854	-
G# / Ab	25.957	51.913	103.826	207.652	415.305	830.609	1661.219	3322.438	6644.875	13289.750	-
A	27.500	55.000	110.000	220.000	440.000	880.000	1760.000	3520.000	7040.000	14080.000	-
A# / Bb	29.135	58.270	116.541	233.082	466.164	932.328	1864.655	3729.310	7458.620	14917.240	-
B / Cb	30.868	61.735	123.471	246.942	493.883	987.767	1975.533	3951.066	7902.133	15804.266	-