Speech Intelligibility
by Ray Rayburn
The spoken word can be challenging to amplify with clarity. While you can't control the diction and enunciation of the person talking, you can try to mic them so as to optimize the intelligibility of their voice, and minimize aural distractions. If they hand hold their microphone, try to get them to hold it close to their mouth, but out of the direct path of their breath to avoid P-Popping and other distracting sounds. Some mics and some talkers may require a windscreen on the microphone to avoid P-Popping.
Gooseneck mics are often used at pulpits or lecterns, particularly when many different talkers may use the same lectern. As long as the talkers do not push the mic away or stand far back from the lectern a gooseneck mic can often pick up speech with clarity.
Lapel mics or worse yet surface mounted or boundary mics are not as desirable since the mic is further from the mouth, and therefore it is harder to get the needed speech level without feedback.
Best are headset or earset types of mics since they get the mic very close to the mouth, and the distance and positioning does not change as the talker moves. Very tiny mics that are almost invisible and hang from one ear were pioneered by Countryman with their E6 models. Today you can get similar mics from many companies.
Once you have the best possible sound from the microphone, you need to process it correctly. Speech has little content below about 125 Hz, with a very deep bass voice going down to maybe around 80 Hz. Rooms, however, often have a lot of noise at lower frequencies from ventilation systems, traffic, and other sources. Because of the way human hearing works, we don't hear softer low frequency sounds. If they get amplified, however, they can become audible and annoying. Therefore using low cut filters on voice microphones is important. Some mics have such filters, and many mixers have a switchable low cut filter on each input. If your mic or console has such a filter, try it and see how it can remove some of the low frequency "mud" from the sound.
The most important frequencies for speech intelligibility are in the range from 1000 to 4000 Hz. If your mixer has a mid frequency EQ try setting it to around 3000 Hz and applying a slight boost. Often a boost of just 2 or 3 dB will provide a subtle but distinct improvement in speech clarity. Don't overdo the boost since too much can make the voice sound sibilant and nasty.
If you are amplifying someone with a very large dynamic range such as a preacher who likes to shout, you can be faced with the challenge of providing enough boost on the softer parts to make them clearly audible, while not letting the loud parts get so loud that it hurts people's ears. To some extent you can control the levels by being very alert and keeping your hand on the level control, but it is hard to react fast enough when the levels get loud when you were not expecting them. This is where a compressor can be a great aid. Set the compressor for a moderate compression ratio such as 3:1 and adjust the compression threshold so with normal levels the compressor is just doing a couple of dB of gain reduction. When the talker suddenly raises his voice, the compressor will reduce the gain, and do so much faster than you could have changed the level adjustment.
Try these simple techniques and you will improve the clarity of the Word in your House of Worship.
Ray A. Rayburn
Ray@K2Audio.com
http://www.K2Audio.com/
