Measure the frequency of any sound in hertz (Hz) with your microphone: a voice, an instrument, a whistle or a test tone. This free online frequency detector shows the frequency, the nearest musical note and cents, and a live spectrum of every frequency from 20 Hz to 20 kHz.
Frequency Detector
Note – – cents
Press Start and make a sound
Microphone off. Nothing is recorded or uploaded: sound is analysed in your browser.
- Minimum
- –
- Maximum
- –
- Average
- –
- Strongest peak
- –
- Time
- 0:00
Strongest frequencies
- The five loudest frequencies appear here.
Settings
Related Tools
- Spectrogram Viewer
See how the frequencies of a sound change over time.
- Frequency to Note Converter
Type a frequency, get the note and cents.
- Voice Hz Test
Find the average frequency of your speaking voice.
- Chromatic Tuner
Tune any instrument: sharp, flat or in tune.
It is useful for checking vocal frequencies, testing instrument tones, measuring a test tone or finding the dominant frequency of any sound. If you mainly want the musical note rather than the Hz value, the online pitch detector gives a more note-focused view.
How to Use the Online Frequency Detector
- Press Start and allow microphone access when your browser asks.
- Stay quiet for a moment while the detector measures the background noise.
- Make a steady sound near the microphone: sing a vowel, play a note, whistle or play a test tone.
- Read the frequency in Hz, the nearest note and the cents value. The label below tells you whether it is the fundamental (pitch) or the strongest peak.
- Press Freeze to hold a reading, then Copy it or download all readings as a CSV file. Press Stop when you are finished.
For the clearest reading, use one sustained tone at a time. A sung vowel, guitar string, piano note or tuning fork gives a more useful result than speech, percussion or background music.
Understanding Your Frequency Result
Frequency is how often a vibration repeats each second, measured in hertz. A stable reading of 440 Hz means the sound repeats about 440 times per second. In standard tuning (A4 = 440 Hz), 440 Hz is the note A4; compare other values with the musical note frequency chart.
| Reading | What it means |
|---|---|
| Frequency (Hz) | The main frequency right now, with sub-hertz precision |
| Note and cents | The nearest note and how far the sound is from it; 100 cents = one semitone |
| Fundamental or strongest peak | Voices and instruments show their fundamental (the pitch you hear); pure and very high tones show the loudest frequency |
| Minimum, maximum, average | The lowest, highest and mean frequency since you pressed Start |
| Strongest peaks | The five loudest frequencies with their notes and levels |
| History | The frequency over the last 20 seconds, to see drift, slides and vibrato |
Cents show whether a sound is slightly sharp or flat; see what cents mean in music tuning.
Frequency Analyzer: See Every Frequency at Once
Under the main reading, the built-in spectrum analyzer draws the level of every frequency from 20 Hz to 20 kHz on a logarithmic scale, and marks the strongest peaks with their values. It works like a frequency analyzer app: a pure tone shows one sharp peak, a voice or instrument shows a row of peaks (the harmonics), and noise shows a broad hill with no clear peak.
Use it to find a hum at 50 or 60 Hz, check a speaker or subwoofer with a test tone, spot a ringing resonance in a room, or see the overtones of an instrument. To see how the spectrum changes over time, open the same sound in the spectrogram viewer.
Frequency Meter: How the Measurement Works
The detector works as a free online frequency meter. For pitched sounds it uses the McLeod pitch method, which finds the period of the waveform and refines it between samples; for pure and high tones it reads the peak of a high-resolution spectrum and interpolates between frequency bins. In our tests steady tones read within 0.1% (440.0 Hz for 440 Hz, 1,000 Hz for 1 kHz, 12,000 Hz for 12 kHz), and white noise gave no false frequency.
Settings let you choose Auto, Fundamental only or Strongest peak only, change the A4 reference, pick another microphone and set the room to quiet or noisy.
Frequency vs Pitch: What Is the Difference?
Frequency is a measurable physical property in Hz; pitch is how high or low we hear a sound. For a steady tone, a higher fundamental frequency sounds higher. Real voices and instruments contain several frequencies at once, and the strongest one is not always the pitch you hear. The difference between pitch and frequency explains this in more detail.
Fundamental Frequency and Harmonics
If you sing a note with a fundamental around 220 Hz, the sound also contains energy near 440, 660 and 880 Hz. These harmonics give the tone its colour. A detector must follow the fundamental rather than a stronger upper harmonic, which is why simple detectors sometimes jump to double the expected value. The article on why tuners show multiple notes explains why this happens, and the strongest peaks list lets you see the harmonics yourself.
Measuring Voice Frequency
Hold a comfortable vowel such as “ah” at a steady volume. Normal speech moves between pitches all the time, so for your average speaking frequency use the voice Hz test instead. A live reading helps you see:
- how stable a sustained note is
- whether your pitch drifts up or down
- the fundamental frequency of your vocal tone
- how far your frequency moves between notes
For recording and analysing your singing over time, the voice pitch analyzer is more suitable. A single Hz value does not define a voice type or diagnose vocal health.
Using the Detector With Musical Instruments
Play one note at a time and let it ring. Plucked strings fluctuate most during the attack, so wait for the note to settle. If you know the note and need its exact frequency, use the note to frequency converter; for tuning, the chromatic tuner shows sharp, flat and in tune more clearly.
Why Does the Frequency Reading Move Around?
A perfectly fixed number is rare with real audio. Background noise, room reflections, vibrato, weak or breathy input, several instruments at once, strong harmonics and automatic processing in the device can all move the reading. Use a quiet room, keep the microphone at a steady distance and play or sing one sustained tone.
If the result keeps jumping, see why pitch detectors give unstable readings, and how microphone quality affects accuracy when comparing devices.
Accuracy and Limitations
This is a practical browser tool, not a calibrated laboratory instrument. Accuracy depends on the sound and the microphone: a strong, steady tone is easy to measure, while noise, chords and heavy reverb are not. Phone microphones also roll off below about 50 Hz and above about 15 kHz. Frequency is not loudness: to measure decibels you need a sound level meter.
Privacy
The microphone starts only when you press Start, the sound is analysed in your browser, and nothing is recorded or uploaded. Stop ends the microphone session.
Frequently Asked Questions
What does Hz mean in sound?
Hz means hertz, or cycles per second. A 200 Hz sound repeats about 200 times each second.
Can a microphone detect sound frequency?
Yes. The microphone turns air pressure into a digital signal, and software measures how often it repeats. Accuracy depends on the microphone, the sound and the room.
What musical note is 440 Hz?
With A4 = 440 Hz, 440 Hz is A4.
Why does the detector sometimes show double the expected frequency?
A strong second harmonic can be mistaken for the fundamental. Choose “Fundamental (pitch) only” in Settings for voices and instruments.
Can I see several frequencies at once?
Yes: the spectrum analyzer and the strongest peaks list show all main frequencies of the sound, including chords and harmonics.
Can it measure very high or very low frequencies?
It measures from 20 Hz to 20 kHz, but most phone and laptop microphones are weak below 50 Hz and above 15 kHz.