Pitch and cents
A cent is a hundredth of a half step. While you sing freely, the lab measures each held note against the nearest piano note (A = 440 Hz). In the checkup, it measures against the note you heard, and only then shows published ranges. Every harmonic moves by the same number of cents, so a small pitch change looks bigger in the high stripes. The picture's frequency scale is linear.
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Vibrato
Vibrato is a regular wave in pitch. The lab measures its speed (waves a second) and its width (± cents, half the top-to-bottom swing). Classical singers holding a vowel average about 5.4 (men) to 5.9 (women) waves a second, and width averaged about ±71 cents in one study of professionals. Choirs, early music and many styles use less vibrato or none, by choice. The words "slow" and "quick" use the lab's own boundaries, listed under The lab's own choices.
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Drift and slides
Drift is a slow change in pitch while you hold a note; the lab removes the vibrato first and fits a line. A slide (scoop) is a quick pitch change at the start or end of a note. The lab counts a note as settled once it stays within 25 cents of its middle, a lab choice.
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Airy, clear, firm and bright
Three sound measures vote together: H1–H2 (how much stronger the lowest harmonic is than the next), the alpha ratio (energy above 1 kHz against below it: brightness) and CPP (how clearly the tone repeats, versus hiss). They're read only on "ah" below about 300 Hz (a lab choice), because on high notes and on "ee" or "oo" the lowest harmonics follow the vowel. Voice type moves them too (women's H1–H2 reads a few dB higher than men's), but the lab's cut-offs are the same for every voice. The groups overlap a lot, a change under about 3 dB is hard to hear, and a microphone can't tell a firmer sound from a belt.
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Ring
Ring is a band of overtones near 3 kHz that helps a voice carry. The lab measures the singing power ratio: the strongest peak between 2 and 4 kHz against the strongest below 2 kHz. Voice type, loudness, the vowel, the note and the microphone all move it; in one study professional men read several dB above professional women. The words "little", "some" and "strong" are the lab's own cut-offs, the same for every voice, and on notes above about 500 Hz (a lab choice) the lab shows only the number.
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Your microphone
Use the phone's or computer's own microphone, not a Bluetooth headset, which usually switches to phone-call quality. The lab asks the browser to switch off its voice effects; Safari's automatic volume can't be confirmed off. In spoken and held-vowel tests, phones measured pitch about as well as studio microphones, while brightness and ring changed with the device. For progress, use the same device, spot and room.
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How the coach decides
The coach waits for a steady note, then picks one thing to say, changing at most every 4 seconds. It describes the sound and never grades it.
The lab's own choices
These are the lab's settings, not published numbers: the ±25-cent settle band, the 3 dB level warning, the four agreeing readings before a tone word, the 0.8-second closed-note reading, the ring cut-offs, the vibrato speed boundaries (4 and 8 a second), the one-minute automatic stop, and for the checkup: the reference notes, the step timeouts, the dial words' cut-offs (pitch 25 and 50 cents, wander 8 and 15 cents), a phrase note 50 cents or more from its note counted as nearer another note (the pitch word is then never "close", nor when a note goes missing), one more try when the pitch moves more than 50 cents in soft-loud-soft, the save reminder (after 5 checkups, or 5 days) and the progress window (21 to 45 days, three checkups) with its spreads (pitch 5 cents, wander 3 cents, clarity 1 dB, balance and ring 3 dB, range 2 semitones); an octave slip (a strong second harmonic) read on the note below; and, on a high note whose vibrato is wider than about 60 cents, a hiss line 2 dB lower. The room-noise limits are published (a voice at least 30 dB above the room is acceptable, 42 dB recommended); the lab's choice is to use the 30 dB limit to switch off tone readings (pitch is still read) and to ask for the held note again.
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Privacy
Your sound is analysed in this browser and then discarded. Nothing leaves this device unless you choose to send a take to Danny. Checkup history stays on this device.
When to see someone
This lab can't tell whether a voice is healthy. If hoarseness or a change in your voice lasts about four weeks without getting better, or if singing or talking hurts, see a voice teacher or a doctor. Go sooner if you sing or speak for a living, and see a doctor straight away for trouble breathing or swallowing. Don't sing through hoarseness; resting quietly is better than whispering. A changing voice in the teens, with cracks and shifting notes, is expected.
