Passion done professionally
Listen. Test. Understand.
Your sound-check companion.
Decibel meter
Live digital level · maximum —
Higher readings mean a stronger captured signal. This uncalibrated phone meter cannot tell you room loudness in dB SPL or whether it is hearing-safe.
Start listening to inspect a peak.
Freeze or use peak hold, tap the graph to inspect, then zoom. Zoom reveals existing FFT detail; it does not add measurement precision.
Tap Listen, then allow your microphone.
Microphone audio stays on this device. No recording.
Feedback buster
No persistent candidate.
A squeal or ring can happen when a microphone hears its own amplified sound. Watch for a narrow peak that persists, then reduce the relevant channel gain first. Move the microphone away from loudspeakers and avoid pointing it toward them. Only adjust EQ when you have verified the cause. Music, test tones and electrical hum can also create persistent peaks: this is a clue, not a diagnosis. Never raise system volume to provoke feedback.
Start quietly.
Turn down your phone and sound system first. Digital level is not a measured output voltage. Avoid headphones, high levels and extreme frequencies. Use short tests.
Phone speakers cannot accurately reproduce all frequencies. Noise is peak-normalized; oscillator peaks may vary slightly with band-limiting. Level is a digital amplitude setting, not acoustic loudness. Timbre changes with the speaker and at high frequencies.
Stops automatically after 10 seconds.
Distance → delay
Converts extra sound-travel distance into delay time. Use it as a starting point when aligning a nearby fill speaker with sound arriving later from the main speakers. Enter the difference in path lengths to the listening position, not simply the distance between speakers. Verify alignment by measurement and listening.
Nominal speaker load
Estimates the combined impedance of speakers wired in series or parallel. Use it to compare a proposed speaker connection with your amplifier’s specified load limits.
Nominal approximation only. Real speaker impedance varies with frequency. Check the amplifier’s minimum load and wiring documentation; this does not confirm compatibility or safe power handling.
Decibels → voltage
Converts a dBu or dBV signal level into RMS voltage. Useful for understanding equipment specifications and matching audio signal levels.
Calculated RMS voltage, not measured. dBFS cannot be converted to volts without interface calibration.
Distance & level
Estimates the change in sound level when you move closer to or farther from a speaker. Useful for planning level differences across an audience area.
Free-field point-source estimate only. Reflections, line arrays and near-field conditions change the result. Not a safe-listening assessment.
Nominal coverage width
Estimates the width covered by a speaker’s stated horizontal angle at a chosen distance. Use it as a starting point for speaker spacing and aiming.
Geometric width on a perpendicular plane, not uniform loudness or guaranteed coverage. Manufacturer beam angles vary with frequency and aiming.
Wavelength & period
Shows the length of one sound wave and the time for one cycle. Useful for understanding phase, path-length differences and room behaviour.
Uses the air temperature above. Wavelength is distance, period is time. Neither automatically determines optimal speaker placement.
Gain ratios
Converts a decibel increase or decrease into voltage and power multipliers. Useful for understanding gain settings and comparing signal or power changes.
Voltage/amplitude and power ratios use different formulas. Comparing voltage as power assumes equal impedance. These are not perceived-loudness ratios.
About this toolkit & safe testing
A practical first version, not a calibrated measurement instrument. It can make mistakes. Verify important readings using appropriate instruments.
The spectrum uses a logarithmic frequency axis and relative digital FFT-bin levels. Frequency resolution and phone microphone response limit what you can see, especially low bass. A peak is not proof of feedback. Frozen data is historical, not live.
Automatic gain control, noise suppression and echo cancellation are requested off, but some browsers or hardware may still process audio. Reported settings are not a calibration. Clipping means the captured digital input is near full scale, not necessarily the mixer itself.
Listening and signal generation never run together. Leaving the page stops audio. Resume manually after a phone call or interruption. Bluetooth adds unknown delay. Never connect mains, speaker outputs or amplifier power outputs directly to a phone. Use suitable test equipment and trained assistance.
Audio is processed locally and never recorded or uploaded. Theme is saved locally. An internet connection is needed to open this first version.
Add JDK Toolkit to your phone
iPhone: Open this link in Safari, tap Share, then Add to Home Screen. If shown, leave Open as Web App on, then tap Add.
Android: Open in Chrome, use its menu and choose Install app or Add to Home screen. The wording depends on your phone.
This is a home-screen web app, not an App Store download. An internet connection is needed to load it. Your microphone permission and settings may need to be set again in the installed app. If an older icon is already saved, remove that shortcut and add it again to see the new icon; do not clear browser data.
We count app openings, control use and workshop-link clicks to improve these free tools. These counters do not store names, contact details, entered values, audio, visitor/device identifiers or session duration.