A technique manages an online meeting. The technique includes providing an audio output signal to a first client device currently participating in the online meeting. The audio output signal directs the first client device to play a particular sound (e.g., a unique tone or a unique series of tones). The technique further involves receiving an audio input signal from a second client device. The audio input signal includes the particular sound. The technique further involves identifying the second client device as being co-located with the first client device in response to the audio input signal which includes the particular sound. Such operation enables the electronic circuitry (e.g., a processing circuit of an online meeting server) to learn whether any client devices are co-located and accordingly associate multiple devices to a single user connected to the online meeting.