About

Incorrect speaker channel assignment is a common wiring fault that degrades spatial audio reproduction. A reversed left/right configuration causes phantom center images to collapse and positional cues in film or gaming audio to mislead the listener. This tool generates a real sine wave at a configurable frequency f (default 440 Hz) and routes it through the Web Audio API's StereoPannerNode to isolate each channel independently. It does not play a pre-recorded file. The oscillator synthesizes the tone in real time at your system's native sample rate.

Use this to verify new speaker installations, diagnose headphone driver failures, or confirm DAC output mapping before critical listening sessions. The tool assumes a standard stereo (2.0) configuration. For surround setups (5.1/7.1), only the front left and front right channels are exercised. Pro tip: if both channels sound identical in volume but one arrives from the wrong physical side, your wiring is reversed at the binding posts or your OS channel mapping is swapped in audio settings.

Formulas

The test tone is generated as a continuous sinusoidal waveform. The instantaneous amplitude y at time t is computed by the Web Audio oscillator as:

y(t) = A ⋅ sin(2πft)

Where A = amplitude (gain, range 0 to 1), f = frequency in Hz, and t = time in seconds.

Channel isolation uses the StereoPannerNode pan parameter p:

p = −1 (full left) | p = 0 (center/both) | p = +1 (full right)

The equal-power panning law applied internally distributes gain as: Left gain = cos(π4 ⋅ (p + 1)) and Right gain = sin(π4 ⋅ (p + 1)). This ensures constant total power across all pan positions.

Reference Data

Test Frequency	Range Category	Typical Use	Notes
100 Hz	Low Bass	Subwoofer / Woofer test	May not be audible on small laptop speakers
200 Hz	Upper Bass	Bass driver response	Good for bookshelf speaker verification
440 Hz	Mid-Range (A4)	Standard tuning reference	Concert pitch. Universally audible
1000 Hz	Mid-Range	Audiometry reference	ISO 226 reference frequency for loudness
2000 Hz	Upper Mid	Vocal presence range	Human ear most sensitive here (Fletcher-Munson)
4000 Hz	Presence	Hearing loss screening	Common noise-induced hearing loss frequency
6000 Hz	Brilliance	Tweeter verification	Tests high-frequency driver response
8000 Hz	High Treble	Sibilance range	Age-related hearing loss starts here
10000 Hz	Very High	Tweeter / DAC quality	Some adults cannot hear above this
12000 Hz	Ultra High	High-frequency roll-off test	Audibility decreases significantly with age
15000 Hz	Near Ultrasonic	Young listener hearing test	Typically inaudible above age 40-50
20 Hz	Infra Bass	Subwoofer low limit	Felt more than heard. Requires capable hardware

Frequently Asked Questions

If you are using open-back headphones or speakers in a reflective room, acoustic crosstalk causes sound from one driver to reach both ears. This is not a tool error. Switch to closed-back headphones or in-ear monitors to isolate channels properly. Also verify your operating system's audio balance is centered (not shifted) in sound settings.

Use 440 Hz as a universal starting point - it is the ISO 16 concert pitch standard and audible on virtually all hardware. For bass driver testing, drop to 100-200 Hz. For tweeter verification, use 4000-8000 Hz. If you hear distortion (buzzing, rattling) at any frequency, it indicates driver damage, loose enclosure components, or clipping at the amplifier stage.

Modern browsers require a user gesture (click/tap) before allowing audio playback - this is the Autoplay Policy. Ensure you clicked one of the test buttons. Then verify: (1) system volume is above 0%, (2) the browser tab is not muted (check the tab icon), (3) the correct output device is selected in your OS audio settings, and (4) no other application has exclusive audio device access (common with ASIO drivers on Windows).

No. The Web Audio API StereoPannerNode operates on a stereo (2-channel) bus only. It can isolate front-left and front-right channels. Center, rear, and subwoofer (LFE) channels require multichannel AudioNode routing via ChannelSplitterNode and ChannelMergerNode with a hardware output supporting more than 2 channels, which most browsers do not expose reliably.

No. Waveform shape (sine, square, sawtooth, triangle) does not affect channel routing - the panning logic is identical. However, sine waves are preferred for diagnostic use because they contain a single frequency (no harmonics), making it easier to identify resonance problems or frequency-specific driver failures. Square and sawtooth waves contain odd and all harmonics respectively, which exercise more of the frequency spectrum simultaneously.

Play the Left Channel test. The sound should come from the speaker physically on your left side when facing the listening position. If it comes from the right, your speaker wires are swapped at the amplifier terminals or the speakers are physically placed on the wrong sides. For headphones, the left cup is typically marked with an L and covers the left ear.