It is unclear if these people
have a permit, but their lack
of clothing is very clear
Whale song - almost everyone's heard it somewhere. It's especially prevalent on new-age CDs, usually combined with the sounds of the pan flute. Scientists don't generally play wind instruments to whales: it's actually illegal to play sounds to whales without a permit in the United States. Recording whale song is not illegal, as long as you don't get closer to the whale than 100 yards. But how does the whale's song get from the whale into your iphone?
|A humpback whale and|
hydrophone, photo by
The applause for "Sound and Pressure" in this video is particularly poignant.
We can't usually feel the pressure of sound waves anywhere but our ears, unless the sound is really loud, like when you stand too close to the speakers at a rock concert.
Quartz, topaz, salt, sucrose (table sugar),
bone, and even silk have piezoelectric
properties. Smashing raw quartz against
the head not recommended to activate
Charged crystals are made up of thousands of molecules, each of which has a positive and negative charge. When the molecules are "relaxed" (when you're not squeezing them), the charges balance out. However, when the crystal is squeezed or bent, the charges are forced together or apart, creating an electronic charge on one side of the crystal. Modern piezoelectrics are generally made of ceramic, which are coated on either side with a thin layer of metal. You can see a modern piezoelectric crystal if you dissect the earpiece on your headphones or a singing card from the grocery store.
|Note: I found an almost identical figure on a creationism site, as evidence of creationism. They claimed as evidence that quartz is the only natural piezoelectric material. As we see above, this just isn't true.|
|Compression of the crystal|
results in a change in electrical
charge, measured in volts (V).
Even when the electrical charge has gone all the way up the cable, and into the boat, it isn't done yet. It still needs to be changed from an analog to a digital signal. Today, we generally use computers and other digital devices (ipods, hard drives, etc) to store our data and music. Analog data is continuous, like a sound wave. Digital data is not continuous - it takes many many samples along a sound wave. In the figure below, we can see the analog sound (in blue) with the digital samples (red). This is probably why many
A great example of analog recording is the vinyl record. If you don't know what a record is, you're either very young or not a hipster. When you play a vinyl record, a needle runs down a continuous groove in the record. As the needle moves down the groove, it vibrates up and down. These vibrations travel up the arm of the record player, and eventually to a piezoelectric crystal (you know this one already!). The crystal converts the vibrations to an electric signal and sends them on to your speakers.
Scanning Electron microscope photograph of the groove
in a record, by Chris Supranowitz.
In contrast, the data on a CD is stored digitally. Each CD is engraved with millions of tiny dots and dashes, which your computer reads with a laser and translates into music.
After an analog to digital converter has changed our electrical signal into thousands of data points, we can finally listen (and look) at the recordings we've made. As it turns out, physics, chemistry, materials and electrical engineering, and biology have all been necessary to get the sound from the whale and into the computer. Whether you're doing yoga (like my friend Sheldon) or desperately trying to finish your thesis, there's a lot of science behind those sounds!
Scanning Electron microscope photograph of a CD,
|Bottlenose dolphin recordings from my acoustic research.|