> ## Content Index > Fetch the complete content index at: https://soundforgepro.com/llms.txt > Use this file to discover other available public pages before exploring further. # Online Pitch Detector: Note, Hz & Cents - URL: https://soundforgepro.com/pitch-detector/ - Published: 2026-08-28T15:03:22.000Z - Updated: 2026-09-04T22:08:36.000Z - Description: Use your microphone to identify one steady note, its frequency and how many cents it sits sharp or flat. Audio stays in your browser. - Author: Erick Finn - Tags: Audio Tools, Audio Fundamentals Press **Start microphone**, allow access and hold one clean note for about a second. The detector shows the nearest note, measured frequency and how many cents the pitch sits sharp or flat. Audio is analysed inside this browser: the page does not record or upload it. Browser pitch tool · local microphone ## Find the note you are playing Your browser asks for microphone access only after Start. Audio is analysed on this device and is not recorded or uploaded. Detector status **Ready** Use one steady voice or instrument note. Chords and noisy rooms can confuse the reading. Start microphone Stop Detected note **—** Waiting for a stable note Frequency**— Hz** Tuning**— cents** Target**— Hz** −50 flat0+50 sharp Input level**— dBFS**0% Pitch confidence**—**0% **Reference pitch**Default A4 = 440 Hz+ A4 reference Hz Reset 440 Ready. Press Start microphone, allow access, then hold one note for about a second. ## How to use the pitch detector 1. **Choose a quiet position.** Move away from fans, loud speakers and other instruments. Reflections and background notes can make the fundamental less stable. 2. **Press Start microphone.** Your browser asks which input it may use. On a phone, point the built-in microphone toward the source without covering it. 3. **Play one sustained note.** A voice vowel, guitar string, piano note or other clear monophonic source works better than speech, percussion or a chord. 4. **Read note, Hz and cents together.** The note name is the nearest equal-tempered pitch. Frequency is the measured fundamental. A negative cents value is flat; a positive value is sharp. 5. **Stop when finished.** Stop releases the microphone track. The page also stops capture when it is hidden or you navigate away. If the reading jumps, don't chase every number. Hold the source steady, bring it closer without clipping the input, and give the confidence bar a moment to settle. The display uses a short rolling median, so an isolated bad frame won't move the note immediately. ## How to read note, frequency and cents | Readout | What it means | How to use it | | ------------- | ----------------------------------------------------------------- | --------------------------------------------------------- | | Note + octave | The nearest note in twelve-tone equal temperament | Identify the pitch region, such as A4 or E2 | | Frequency | The estimated fundamental in cycles per second | Compare the measured Hz with the target | | Cents | The logarithmic distance from the nearest target note | Negative is flat, positive is sharp; zero is centred | | Input level | The microphone signal level inside the digital input | Move closer if too quiet; move back if the input distorts | | Confidence | How clearly the current frame supports one repeating pitch period | Treat low-confidence note names as provisional | One semitone contains 100 cents, so a reading near +50 is halfway from the displayed note toward the next semitone. Cents are logarithmic: the same musical interval uses the same cents distance at low and high frequencies. That said, the number is still an estimate; don't expect every phone microphone or noisy room to resolve the pitch to laboratory precision. ## When to change the A4 reference The default is A4 = 440 Hz. Leave it there for ordinary modern tuning checks. Open **Reference pitch** only when an ensemble, recording, historical practice or supplied brief uses another reference. Changing A4 changes the target-note map; it doesn't change the audio captured by the microphone. For example, at A4 = 440 Hz the A below middle C is 220 Hz and the A above it is 880 Hz. Every octave doubles or halves frequency. Other notes follow the equal-tempered ratio of the twelfth root of two. If you need to create a known reference rather than measure one, use the [online tone generator](https://soundforgepro.com/online-tone-generator/). Keep its output quiet and use a second device if you want to test this detector without creating microphone feedback. For a static equal-tempered lookup across octaves, use the [musical note frequency chart](https://soundforgepro.com/musical-note-frequency-chart/). ## Sources that work well — and sources that do not - **Voice:** sustain one vowel at a comfortable level. Spoken sentences change pitch too quickly for a stable tuner-style reading. - **Guitar and bass:** pluck one string and let the initial attack pass. Use the settled body of the note; overtones and fret noise can dominate the first instant. - **Piano and keyboards:** play one note. The sharp attack may jump briefly before the sustained tone settles. - **Wind and bowed instruments:** hold one steady note with consistent breath or bow pressure. - **Chords:** not supported as chord recognition. Several fundamentals and overtones compete, so the result may jump between partials. - **Drums, clicks and noise:** usually unsuitable. A transient or broadband signal does not provide one persistent fundamental period. The supported display range is deliberately limited to roughly 65–2,000 Hz. That covers common voice and instrument fundamentals while leaving enough samples for useful browser analysis. Frequencies outside the range may appear as silence, a harmonic or an unstable result. For a full view of energy across many simultaneous frequencies, use the [audio spectrum analyzer](https://soundforgepro.com/audio-spectrum-analyzer/); it answers a different question from this note detector. ## How the browser estimates pitch The page reads short microphone frames through the Web Audio API and applies a YIN-style fundamental-frequency estimate. The original [YIN pitch-estimation paper](https://pubmed.ncbi.nlm.nih.gov/12002874/) describes a difference function and cumulative mean normalization designed to reduce common autocorrelation errors. Here, a confidence threshold rejects weak or ambiguous frames, and a short median smooths accepted frequencies before note conversion. The detected frequency is converted to an equal-tempered MIDI-note position relative to the selected A4 reference. The nearest integer identifies the note; the remaining logarithmic distance becomes cents. The algorithm runs in page memory, and the microphone source is connected to an analyser rather than the audio output, so the page shouldn't play your input back through the speakers. Browser microphone capture is available only in a secure context and requires explicit permission, as documented for [MediaDevices.getUserMedia()](https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getUserMedia). Mobile browsers can also suspend Web Audio until a user action, so the page creates and resumes its audio context inside the Start action, consistent with [AudioContext.resume()](https://developer.mozilla.org/en-US/docs/Web/API/AudioContext/resume). ## Why the pitch reading jumps or stays blank - **Permission blocked:** allow microphone access for soundforgepro.com in the browser’s site settings, then press Start again. - **No signal:** confirm the selected microphone works, move the source closer and check that another app is not holding the input. - **Signal too quiet:** reduce the source-to-microphone distance. Do not boost until the room noise becomes louder than the note. - **Reading jumps by an octave:** wait past the attack, play more softly or change microphone position. A strong harmonic can briefly look more periodic than the fundamental. - **Wrong note during a chord:** isolate one note. This page is a monophonic pitch detector, not a chord detector or key finder. - **Phone does nothing after Start:** reload the HTTPS page, make sure the browser has microphone permission and press Start again from the visible button. Private or embedded browsing modes can apply stricter permission rules. ## Where pitch detection fits an editing workflow Pitch detection is useful before a destructive edit: identify a sustained tone, compare a suspected hum with a musical partial or document the note before time/pitch processing. It won't repair the audio, though. For recorded material, inspect the spectrum as well, then make the change in your editor and measure again. If you're changing pitch or duration in Sound Forge, the [time-stretch and pitch-shift guide](https://soundforgepro.com/time-stretch-pitch-shift-sound-forge/) separates musical transposition from duration changes and explains where artifacts tend to appear. Use the tone generator for a fixed test signal and the spectrum analyzer for broadband peaks; this detector is for one live fundamental. ## Privacy and measurement limits - The page requests microphone access only after you press Start. - It does not create a recording, upload audio or connect the microphone to speaker output. - Stop, page hide and navigation release the active microphone track. - The reading depends on the source, room, microphone, sample rate and browser. - It is not a calibrated frequency counter, hearing test, vocal-range diagnosis or proof of instrument intonation. ## Online pitch detector FAQ ### Does the pitch detector record or upload my voice? No. The live MediaStream is analysed in the current browser tab. The page does not create a recording, send audio to a server or play the microphone signal through the output. ### What does a negative cents reading mean? A negative value means the measured pitch is flat relative to the nearest displayed target; a positive value means it is sharp. Zero is centred. One semitone equals 100 cents. ### Can it detect guitar, bass, piano and voice? It can estimate a stable single fundamental from those sources when the note is clear and inside roughly 65–2,000 Hz. Let sharp attacks settle and avoid playing more than one note at once. ### Can this tool identify chords or a song key? No. It is a monophonic pitch detector. Chord recognition and key estimation require analysis of several simultaneous or time-varying pitches and are separate tasks. ### Why does the detector show the wrong octave? A strong overtone, noisy attack, very low note or weak fundamental can produce an octave error. Hold one note, wait past the attack, adjust microphone position and use the confidence reading before trusting the result. ### Should I change A4 from 440 Hz? Keep 440 Hz unless the ensemble, recording or delivery brief uses another reference. Changing A4 remaps the target frequencies and cents values; it does not alter the captured sound.