In visible recordings, a speaker knows that he is being recorded. This knowledge has an impact on the speech produced: speaker stress phenomena such as a more formal style of speech, a high rate of errors, unnatural pronunciation and prosody can be observed. The environment in which the speaker produces speech, and the task the speaker is asked to perform also determine the style of speech to a large extent.
In many real world situations and applications microphones are present - use of the telephone, dictation , speaking in radio or television studios , traffic guidance, e.g. flight control, etc. Speakers in these situations are used to microphones , and the speech they produce is adapted to the task at hand. In these cases, visible recordings should pose no problems.
In general, if speakers are asked to perform a task that requires some cognitive activity , they quickly forget that they are being recorded. Thus visible recordings can be used even for recording very natural and spontaneous speech if the speaker feels comfortable in the recording situation and is occupied by the task to be solved.
Visible recordings are usually made in recording studios or in environments set up specifically for the recording, e.g. sample office rooms, application simulations, etc. Hence, most recording parameters such as microphone calibration and positioning, recording equipment, can be chosen for maximal quality.
The major advantage of visible recordings is that the recording itself can be monitored on-line to ensure a high technical quality of the recording. Furthermore, speakers have in general agreed to being recorded prior to the recording, so the risk of producing material that may not be used is greatly reduced.