Video screens are increasingly present in publicly accessible or publicly viewable places. Including in shop windows, bars and restaurants, buses and trains, and also as electronic billboards.
Often there might be no audio associated with the video being shown on the screen. Or the audio might not be audible to someone watching the screen. The reasons are several. One is that the owner of the screen might not be allowed to broadcast accompanying audio. For example, consider a billboard located outdoors. The broadcasting of audio might be considered too awkward or intrusive to pedestrians.
Another reason is that there might be a limit on the maximum volume of the audio that can be broadcast, where the limit is set by technology or local regulation. For example, a shop window containing a screen might have speakers or some other technology that can play audio only discernible to those very close to the window. Another example is in a bar. Some bars might have an ambient noise level loud enough that someone watching the video cannot hear the audio, even though the audio is being played. Another example could be a screen in a bus. For safety or convenience to the passengers and driver, there might be a maximum volume to the screen's audio. Or the audio speaker might be defective or turned off by the driver.