Peak Frequency Detector
Instantly find the loudest frequency in any sound. See the peak Hz value in a giant display, view the top 5 strongest frequencies ranked by level, track peak hold across your session, and get instant noise diagnosis cards — all processed locally in your browser.
Peak Frequency Detector Tool
Or drop an audio file here to analyze —
MP3, WAV, OGG, FLAC — max 50 MB
| # | Frequency | Note | Band | Level (dB) |
|---|---|---|---|---|
| Start listening to detect peaks | ||||
| Time | Peak Hz | Note | Band | dB |
|---|
How to Use the Peak Frequency Detector
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Start Listening
Click "Start Listening" and grant microphone permission. Choose your preferred microphone from the dropdown. The tool begins scanning for the loudest frequency immediately.
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Read the Giant Hz Display
The large number shows the single strongest frequency in your audio signal, along with its musical note name and frequency band classification (sub-bass, bass, mid, treble, etc.).
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Check the Top-5 Peaks Table
Below the main display, the Top 5 Strongest Frequencies table shows additional peaks with their Hz, note, band, and level. This helps identify all significant frequencies in complex sounds.
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Review Noise Diagnosis
The Noise Diagnosis card automatically matches common noise sources (mains hum, HVAC, ground loop, etc.) and provides actionable troubleshooting advice based on the detected peak frequency.
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Copy or Export Results
Use 📋 Copy Peak Frequency for instant clipboard access, or 💾 Export CSV to download your full session history for documentation.
Understanding Your Results
Peak Frequency (Hz)
The main display shows the single loudest frequency component in the audio signal. This is the frequency with the highest amplitude in the FFT spectrum. Parabolic interpolation refines the reading beyond the raw FFT bin resolution for sub-Hz accuracy.
Top-5 Peaks
The peaks table shows the 5 strongest frequency components ranked by amplitude. Each peak must be at least 100 Hz apart to avoid listing harmonically-related duplicates. This helps identify multiple noise sources or harmonic content.
Frequency Bands
Each frequency is classified into a standard audio engineering band: Sub-Bass (20–60 Hz), Bass (60–250 Hz), Low Mid (250–500 Hz), Mid (500–2k Hz), Upper Mid (2k–4k Hz), Presence (4k–6k Hz), and Brilliance (6k–20k Hz). The band energy bars show how energy is distributed across these ranges.
A-Weighting
When enabled, A-weighting adjusts the spectrum to match human hearing perception. Low and very high frequencies are de-emphasized because humans are less sensitive to them. This shows which frequency sounds loudest to you rather than which has the highest raw amplitude.
Noise Diagnosis
The tool includes a database of 30+ common noise signatures. When the peak frequency matches a known noise source (e.g., 60 Hz mains hum, 120 Hz ground loop, HVAC fan frequencies), it displays an identification card with the likely source and suggested fix.
Peak Hold
The Peak Hold value tracks the highest frequency detected during the entire session. This is useful for capturing transient peaks that appear briefly and might be missed on the live display.
How Peak Frequency Detection Works
Finding the loudest frequency in a complex sound requires transforming the audio signal from the time domain into the frequency domain. This tool uses the Fast Fourier Transform (FFT) to decompose the audio into its constituent frequency components.
FFT Analysis
The Web Audio API's AnalyserNode computes the FFT in real time. With the default FFT size of 8,192
at a 48 kHz sample rate, the frequency resolution is approximately 5.86 Hz per bin. Increasing
the FFT size to 16,384 doubles the resolution to ~2.93 Hz, which is important for distinguishing closely-spaced
low-frequency noise sources (e.g., 50 Hz vs 60 Hz mains).
Parabolic Interpolation
Raw FFT bins give discrete frequency values. To achieve sub-bin accuracy, the tool applies parabolic interpolation using the three bins around each peak (the peak bin and its two neighbors). This refines the frequency estimate to within ±0.5 Hz even with moderate FFT sizes.
A-Weighting Curve
The optional A-weighting filter applies the IEC 61672 frequency response curve, which approximates the sensitivity of the human ear at moderate listening levels. It attenuates frequencies below 500 Hz and above 6 kHz, boosting the mid-range where human hearing is most sensitive. This is the same weighting used in professional sound level meters (dBA).
Noise Source Matching
The diagnostic engine maintains a lookup table of common noise frequencies and their sources. When the peak frequency falls within a known range, the tool displays the likely source and a suggested remedy. This covers electrical hum (50/60/100/120 Hz), HVAC systems, fluorescent lighting, computer fans, and more.
Frequently Asked Questions
What is the difference between peak frequency and dominant frequency?
The peak frequency is the single frequency with the highest amplitude in the spectrum at any given moment. The dominant frequency typically refers to the fundamental pitch of a sound, which may not always be the loudest component (harmonics can be louder than the fundamental). This tool shows the raw peak — the loudest frequency, regardless of whether it's a fundamental or harmonic.
Why does my room show a 60 Hz (or 50 Hz) peak?
A persistent peak at 60 Hz (North America, Japan) or 50 Hz (Europe, Asia, Africa) is almost always electrical mains hum picked up by your microphone or audio cable. The harmonics at 120 Hz / 100 Hz are also common. This is normal and typically caused by electromagnetic interference from power lines, transformers, or unshielded cables.
What does A-weighting do and when should I use it?
A-weighting adjusts the readings to match how humans perceive loudness. Low-frequency sounds (below ~500 Hz) and very high frequencies (above ~6 kHz) sound quieter to our ears than mid-range sounds at the same level. Turn A-weighting on when you want to know which frequency sounds loudest to you, and leave it off when you want the raw, unweighted physical measurement.
How accurate is the peak frequency reading?
With the default FFT size of 8,192, raw accuracy is ±3 Hz. With parabolic interpolation enabled, accuracy improves to approximately ±0.5 Hz. For even better resolution, switch to FFT size 16,384. Accuracy also depends on your microphone quality and ambient noise conditions.
Can I use this to diagnose a humming or buzzing noise?
Yes — this is one of the primary use cases. Start listening in a quiet room with the humming noise present. The peak frequency display will show the exact Hz of the hum, and the Noise Diagnosis card will suggest the likely source (mains hum, ground loop, HVAC, etc.) with troubleshooting steps.
What is Peak Hold and how does it work?
Peak Hold remembers the highest peak frequency detected during your entire session. This is useful for capturing transient or intermittent sounds that appear briefly. It resets when you click the Reset button or refresh the page.
Is my audio data private?
Absolutely. All frequency detection and analysis runs 100% in your browser using the Web Audio API. No audio data is ever recorded, transmitted, or stored on any server. The tool works completely offline once loaded.
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