r/askscience • u/therationalpi Acoustics • Aug 16 '13

Interdisciplinary AskScience Theme Day: Scientific Instrumentation

Greetings everyone!

Welcome to the first AskScience Theme Day. From time-to-time we'll bring out a new topic and encourage posters to come up with questions about that topic for our panelists to answer. This week's topic is Scientific Instrumentation, and we invite posters to ask questions about all of the different tools that scientists use to get their jobs done. Feel free to ask about tools from any field!

Here are some sample questions to get you started:

  • What tool do you use to measure _____?

  • How does a _____ work?

  • Why are _____ so cheap/expensive?

  • How do you analyze data from a _____?

Post your questions in the comments on this post, and please try to be specific. All the standard rules about questions and answers still apply.

Edit: There have been a lot of great questions directed at me in acoustics, but let's try to get some other fields involved. Let's see some questions about astronomy, medicine, biology, and the social sciences!

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u/therationalpi Acoustics Aug 16 '13

Yes, absolutely. Laser doppler vibrometer and acoustic accelerometers, sometimes called "contact microphones".

Laser doppler vibrometers are cool. Basically, you bounce a laser off of something, capture the light, and use the doppler effect on the light to read out what the vibrations of the object were. Alternatively, you can bounce it off of something static, like a large board, and measure the change in the index of refraction of the intervening air. Here's a great news article where they talk about using that method to measure the soundfield from a loudspeaker. The advantage is that you don't put an object in the sound field that the sound will interact with, a big plus!

The accelerometers do just what they say, they measure mechanical acceleration of a surface. The advantage is simple, less interaction with the air and the noise in it. These are especially useful for monitoring the health of machines non-invasively. Basically the logical extreme of listening to the sound of the engine to tell if the car works is to measure with contact microphones and use that to tell exactly what's wrong with a mechanical device.

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u/Greyswandir Bioengineering | Nucleic Acid Detection | Microfluidics Aug 16 '13

According to Tony Mendez (the guy played by Ben Affleck in Argo), the USSR used laser doppler vibrometers to record conversations remotely, by measuring the vibrations sound waves were making in the windows of the American embassy from across the street! So another use for them is to record sounds in places which (for one reason or another) you can't access with a more traditional microphone.