Ask Fuzzy: how far can the human voice travel? | Canberra weather



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Almost anyone who is elderly will say that they have a hard time hearing a voice in a noisy room. This is because hearing normally decreases by about one decibel for each year that you get older. If you imagine a wavy line on a graph, you will understand why understanding speech is such a complicated exercise. Add to that the confusing din of a crowd, and it’s no wonder we struggle at times. But if you can hear well, how far away can you hear a voice, even if you don’t know what it is saying? Under ideal conditions, the range of the human male voice is around 180 meters while remaining intelligible. The sound pressure level normally drops by half (six decibels) for every doubling of distance, so you will still be able to hear the speaker’s voice from 360 meters away even if you cannot understand what he is saying. It’s outside, but inside things get tricky because of the acoustics. If you are standing near someone, the voice you hear is dominated by a direct path from them to you. Beyond a meter or so, sound becomes dominated by sounds reflected in the room, making it susceptible to being absorbed by soft surfaces, bounced off hard surfaces, and shaped in other unpredictable ways. In a room with high reverberation, your ears pick up several copies of sound, slightly out of sync depending on how they are reflected in the room. Add a whistling espresso machine and a chatty crowd and things get tough. Therefore, when talking to someone who is hard of hearing, you should stand close and look directly at them. It helps if they can see your face so they can lip read. According to The Guinness of Records, there is a recorded case of a voice heard at a distance of 17 kilometers. It was through calm water at night. You can hear the “whispered wall” effect around some curved dam walls, or visit Questacon where you can communicate a surprising distance using a pair of curved dishes. Or you could be a blue whale, making very low and extremely loud sounds – up to 188 decibels. It is by far the loudest sound produced by an animal (a jet taking off makes about 120 decibels). Another blue whale could hear this more than 800 kilometers away. Listen to the Fuzzy Logic Science Show at 11am Sundays on 2XX 98.3FM. Send your questions to [email protected] Twitter @ FuzzyLogicSci




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