The Science of Sound
• Sounds of Laughter, Shades of Life The birds do it. The bees do it too and so do you. An amazing range of animals generate sound: pressure waves caused by displacing the medium in which they travel.
• Tiny Noisemaker You may think that’s the screaming baby across the airplane aisle, but human speech is at a comfortable 60 dB. The decibel, named after Alexander Graham Bell, is logarithmic in scale: an increase of 10 dB is actually ten times as loud. Anything above 85 dB is dangerously painful and the loudest sound tolerated by the human ear is 120 dB. The loudest animal is the sperm whale at an ear-splitting 236 dB! But the prize for the biggest bang for buck goes to the lesser water boatman: perhaps in protest of its diminutive size and name, it is the loudest animal for its body size (see graph; listen here: http://goo.gl/BHKhl). Fortunately, the surrounding water dissipates 99% of its mating call or it would sound like a freight train hurtling by. Shakespeare may dismiss life as a tale told by an idiot, full of sound and fury, signifying nothing , but to a female water boatman, the call of her mate is irresistible. Especially since he generates the sound by rubbing his…ahem.. sexual appendage against his abdomen. The lesser water boatman’s call is an example of runaway evolution since there is apparently no penalty paid for the price of loudness in his case.
• Cheers to your Ears Astonishingly, the actual displacement of molecules in the air is tiny- about 11μm or 1/7th the thickness of a piece of paper at 120 dB! Did you know that the faintest sound the human ear can detect corresponds to a displacement of air molecules by ~1.1 x 10-11 m, or 11 picometers– about 1/10 the radius of a mid-sized atom? Not only can the human ear detect vibrations with a sensitivity that spans six orders of magnitude, it can also detect sounds across nearly a 10 octave range of frequencies.
Movie Soundtrack : Across The Universe + Helter Skelter (Across The Universe)
Sounds of laughter, shades of life
Are ringing through my opened ears
Inciting and inviting me.
Limitless undying love, which
Shines around me like a million suns,
It calls me on and on across the universe
• Whacky video on how we hear: Fun Science: Sound
• Cool Info on Sound: http://www2.cose.isu.edu/~hackmart/soundwavesIengphys.pdf