Sound versus sight
This is a simple reaction time test: one signal, one response, no choices to make. The only difference from the visual reaction time test is the signal. Here you react to a beep instead of a color change.
Studies usually find that people respond to sound a little faster than to light, though not every study agrees. Jain and colleagues tested 120 medical students aged 18 to 20 on a laptop and recorded the fastest of five tries for each signal. Auditory reactions averaged 228 ms and visual ones 248 ms, about 20 ms quicker for sound (Jain et al., 2015). The same paper quotes older textbook figures of about 160 ms for sound and 190 ms for light in college-age adults, and explains the gap partly by the auditory signal reaching the brain sooner.
| Measurement | Sound | Light | Source |
|---|---|---|---|
| 120 students aged 18–20, laptop, fastest of 5 tries (mean) | 228 ms | 248 ms | Jain et al., 2015 |
| Textbook figures for college-age adults, as quoted by Jain et al. | about 160 ms | about 190 ms | Jain et al., 2015 |
Whether you see that gap on this site depends on your setup. Audio output in a browser adds its own delay, so the advantage can shrink or disappear. Run both tests on the same device, with the same hand and input, and compare like with like.
How this test times the beep
- The beep is scheduled on the audio clock. The Web Audio API lets the page start a sound at an exact time on the audio hardware's clock. The test schedules the beep 2 to 5 seconds ahead, at random, so it does not depend on when a JavaScript timer happens to fire.
- The audio clock is mapped to the page clock. Where supported,
AudioContext.getOutputTimestamp()reports which audio frame the output device is playing and when, on the same clock asperformance.now()(MDN). The test uses it to work out when the beep actually left the device. If that is not available, it adds the browser's reportedbaseLatencyandoutputLatencyto the scheduled time instead (MDN). The result screen tells you which method your browser used. - Your press uses the input event's own timestamp, not the moment the script got round to handling it.
- False starts are redone. A press before the beep, or less than 100 ms after it, is not scored. The 100 ms line comes from sprint starting rules. Pain and Hibbs did measure some sprinters reacting to the gun in under 100 ms, but with force sensors in the blocks (Pain & Hibbs, 2007). With browser input and audio lag on top, a real response that fast is very unlikely here.
- Missed beeps are redone too. If there is no press within 2 seconds, the round restarts and the screen asks you to check your volume.
What it cannot correct for: delay that your operating system or headphones add without telling the browser, and the lag of your keyboard, mouse or touchscreen. Like any browser test, it will read slower than a lab measurement.
Why Bluetooth headphones skew the result
Bluetooth audio is compressed, sent over radio, buffered and decoded before you hear it. Developer Stephen Coyle measured the time from a tap on an iPad to the sound and got 274 ms for first-generation AirPods, 178 ms for the second generation and 144 ms for AirPods Pro (Coyle, 2019). Those were his measurements on one device, and the totals include the iPad's own touch and audio processing. Still, they are many times larger than the roughly 20 ms gap between sound and sight you might be trying to see.
Browser audio timing also varies with wired output. In a large timing study, audio-visual synchrony was the least precise part of browser-based experiments, and one platform showed audio lags above 100 ms in three of the browser setups tested (Bridges et al., 2020). Use wired headphones or built-in speakers, and keep the same setup when you compare results.
Getting a clean result
- Use wired headphones or the device's own speakers, at a volume where the beep is clear but comfortable.
- Pick a quiet room and close other tabs or apps that play sound.
- Rest a finger on the key, mouse button or screen before each round so you are not also moving your hand into place.
- Don't try to count the wait. It is random, and guessing only gets you false starts.
- Do two or three runs and look at the median as well as the best. One quick round can be luck.
- If you hear nothing on an iPhone or iPad, check the volume and the silent switch, then use Test the sound before starting.
Audio reaction time FAQ
- Is reaction time to sound faster than to sight?
- Usually, yes. In a study of 120 students aged 18 to 20 tested on a laptop, the fastest of five auditory reactions averaged 228 ms against 248 ms for visual ones, about 20 ms quicker. In a browser, audio output delay can cancel some or all of that advantage.
- Why do Bluetooth headphones matter?
- Bluetooth audio is encoded, sent over radio, buffered and decoded before you hear it. One developer measured 144 to 274 ms between a tap and the sound on different AirPods models. That delay is larger than the differences this test is meant to show, and the browser cannot always see it. Use wired headphones or speakers.
- What counts as a false start?
- Pressing before the beep is audible, or less than 100 ms after it. 100 ms is the line sprint starts use for false starts. The round is redone and not scored.
- Why does nothing change on screen when the beep plays?
- On purpose. If the screen changed at the same moment, you could react to what you see instead of what you hear, and it would no longer be an audio test.
- Why is my result slower than the lab numbers?
- Browser tests include delays a lab setup removes: audio output buffering, input device and operating system lag, and the browser's event handling. In timing studies with robot-pressed keys and screens, browsers recorded responses 57 ms or more late on the phones, tablets and laptops tested (Pronk et al., 2020), and about 80 ms late on average in another study (Anwyl-Irvine et al., 2021).
Sources
- Jain A, Bansal R, Kumar A, Singh KD. A comparative study of visual and auditory reaction times on the basis of gender and physical activity levels of medical first year students. International Journal of Applied and Basic Medical Research. 2015;5(2):124–127. doi:10.4103/2229-516X.157168
- Pain MTG, Hibbs A. Sprint starts and the minimum auditory reaction time. Journal of Sports Sciences. 2007;25(1):79–86. doi:10.1080/02640410600718004
- Bridges D, Pitiot A, MacAskill MR, Peirce JW. The timing mega-study: comparing a range of experiment generators, both lab-based and online. PeerJ. 2020;8:e9414. doi:10.7717/peerj.9414
- Pronk T, Wiers RW, Molenkamp B, Murre J. Mental chronometry in the pocket? Timing accuracy of web applications on touchscreen and keyboard devices. Behavior Research Methods. 2020;52(3):1371–1382. doi:10.3758/s13428-019-01321-2
- Anwyl-Irvine A, Dalmaijer ES, Hodges N, Evershed JK. Realistic precision and accuracy of online experiment platforms, web browsers, and devices. Behavior Research Methods. 2021;53(4):1407–1425. doi:10.3758/s13428-020-01501-5
- Coyle S. AirPods Pro latency measurements (2019). stephencoyle.net/airpods-pro
- MDN Web Docs. AudioContext: getOutputTimestamp() method. developer.mozilla.org
- MDN Web Docs. AudioContext: outputLatency property. developer.mozilla.org
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