Posted by: Andrew | February 9, 2010

You say “Bayta” and I’ll say “Beeta”

I was preparing my lecture on sound for tomorrow and this includes measuring the sound intensity level using the decibel scale.  It’s really a comparison between two different sound intensities, one of which is often taken as the limits of human hearing. The equation is

The sound intensity level is given by the Greek letter “Beta”.   Now, in England we pronounce this with a long E sound – “Beeeeta”, but in Canada, it’s pronounced with an “ay” sound – “Bayta”.  I always make a joke about this, and all the other greek letter pronounciations which follow the same pattern (eta, theta, zeta…).

I think the Canadian pronounciation must come from the Scottish influence, as my  math teacher at Lady Manners (Mr. Wilkie) was a Scot, and he pronounced it “Bayta” too.   The students just have to get used to my pronounciation.  It broadens the mind to realize that the English language is a broad church with lots of regional variations.

Note that the decibel scale is a logarithmic one, so if you increase the intensity of the sound by a factor of 2, then you only get an increase of 3 dB.  The variables I and I0 are the intensities being compared.  The physics terminology is very confusing – it is extremely easy to mix up the intensity (measured in Watts per square metre) and the sound intensity level (measured in decibels).

I usually also have some fun with the students.  We have a hand held decibel meter, so that I can measure the sound intensity level in the lecture theatre. I get the students to shout “We love Physics“.  I can usually get about 70-75 dB.   Then I get them to chant “We hate Physics”.  This always gets a stronger emotional response, a louder shout and notably higher decibel reading.

I will also be warning about the effects of listening to personal stereos with the volume set too loud. Number 2 son had to visit the audiologist a few years ago, and she told me that they were seeing an epidemic of young people with permanently damaged hearing, probably caused by listening to personal stereos with the volume set too high. I will be showing a BBC news article about Pete Townsend, the lead guitarist with The Who, who has permanently damaged hearing because of the loud rock music. The Who probably hold the record for the loudest ever rock concert. The Who were the half time entertainment at the Superbowl last night, so this is quite topical. I’ve got a very good monochrome video clip of them playing “Substitute” from 1966, when they were really in the “Mod” style. I’ll probably use it to round off the class tomorrow.

I’m trying to make things easy for the students this week, as they have their midterm physics exam coming up on Thursday evening, and probably exams in other subjects as well.

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