Intelligibility - Classroom Audio Systems

When talking about classroom audio systems or any audio system for training environments, the key objective is intelligibility. Intelligibility is just what it sounds like, the quality of being intelligible or understandable.

Audio that is intelligible has the quality of clarity, it has a “crispness” about it. The opposite of intelligible audio is sometimes referred to as the “Peanuts” effect. When Charlie Brown was talking to an adult, all you could hear was “Wha whu waa waa whu wha”. A similar effect can be heard when someone has a TV turned up in the room next to you with the door closed. Speech becomes muffled, not very intelligible. Why? Because some of the frequencies that make speech intelligible are being muted while some of the other frequencies are coming through the wall and door more effectively. As we know, bass carries and higher frequencies diminish much more quickly.

Studies have shown that most of speech intelligibility comes from hearing consonants clearly. The sounds “ch” and “sh” and the consonants b, c, f, h, k, p, q, s, t, and x are among the higher frequency sounds that make words intelligible. Whereas vowels tend to carry well and easily at lower frequencies, typically from 100Hz to 280Hz. The fascinating part is that the human ear tends to be most sensitive to frequencies around 3000Hz and this is the range where the above consonants can typically be heard when pronounced clearly and properly. Most cell phones and even land lines have a hard time transmitting frequencies much over 4000hz. You may have noticed that it can be difficult to understand people over the phone, when you have no problem at all hearing them in person. Above 4000hz there is still a lot of audio that promotes speech intelligibility. Really, frequencies up to 8000Hz play a strong roll in enhancing speech intelligibility.

What makes things more challenging is that kids today frequently have slightly impaired hearing for frequencies above 3000Hz. Yes, too much music played too loudly. I guess our grandparents were right when they said rock n’ roll would make us dumber.

So what works when it come to classroom audio systems and getting the best bang for the buck? You need a system that handles higher frequencies with respect. You don’t want a “muffled” system. When Roemtech designs a classroom audio system, we always put speech intelligibility at the top of the list. You need speakers and amplifiers that accurately recreate the higher frequencies found in the speech range. That’s one reason all of our speakers have dedicated tweeters. For more information, check out our “Speakers” page. You’re going to like what you hear!

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