krug3r
21-08-2003, 10:54
People could soon have no excuse for bellowing into their phones on trains. Korean engineers have de signed a tiny microphone that picks up whispers, even in a noisy environment. Whispers into a standard mobile phone are easily drowned out by other sounds and tend to exaggerate consonants such as s, t, p and b. Holding the mouthpiece closer makes things worse.
The new set-up uses a filter to cut the air-blow effects of problematic sounds. The prototype is small enough to fit into a typical cellphone, say the developers Sungjoon Choi and colleagues at the Pohang University of Science and Technology in Kyungbuk.
The filter, fixed to a plate with a microphone at each corner, has a perforated central panel by the speaker's mouth. The holes let air through, so pressure spikes from air puffs don't register in the microphones.
Choi's team reduced blowing further by pointing the microphones away from the speaker. Such multi-microphone systems have been used for decades to make sound pick-up more directional. But they didn't work in cellphones, where the sound source is close to all the microphones.
To solve this, the team devised a signal-processing method that filters out everything but the sounds made directly around the mouthpiece.
The new set-up uses a filter to cut the air-blow effects of problematic sounds. The prototype is small enough to fit into a typical cellphone, say the developers Sungjoon Choi and colleagues at the Pohang University of Science and Technology in Kyungbuk.
The filter, fixed to a plate with a microphone at each corner, has a perforated central panel by the speaker's mouth. The holes let air through, so pressure spikes from air puffs don't register in the microphones.
Choi's team reduced blowing further by pointing the microphones away from the speaker. Such multi-microphone systems have been used for decades to make sound pick-up more directional. But they didn't work in cellphones, where the sound source is close to all the microphones.
To solve this, the team devised a signal-processing method that filters out everything but the sounds made directly around the mouthpiece.