Level is capped for comfort. To meaningfully disrupt a nearby recorder, noise must approach the loudness of the speech — which also makes it hard for people to hear you.
This degrades, it does not defeat, AI transcription. Modern speech recognisers are trained to remove steady noise. Babble mode masks better than white noise, but the only reliable method is ultrasonic hardware — which browser speakers cannot produce.
Deliberately corrupting someone's recording can intersect with local recording-consent and wiretap laws. Check your jurisdiction. This tool runs offline and never touches your microphone.