Although he has a long list of inventions, he is best known as the inventor of the telephone. Although born in Scotland, he emigrated to Canada at age 23. Decibels are named in honour of scientists, engineer and inventor Alexander Graham Bell (1847-1922). With sound it is conventional to establish a reference level of 0 dB at an intensity of 1.0x10 -12 W/m 2, the approximate limit of human hearing.
For example if one sound level was 1000 times another, that would be a 30 dB difference. More specifically we use dB in sound to compare the sound intensity values (W/m 2). The decibel is used to compare two power levels, with the dB difference being 10 times the logarithm of the ratio of the powers. At a more advanced level students might use the app to investigate how intensity levels decrease at different distances from a source, or study sound levels from two speakers driven with the same tone in order to quantitatively study interference effects.Ī bit of background on decibels (dB). As mentioned at the outset, the operation of the app is so straightforward that I can see appropriate use by students of all ages, and the general public. If the students note where they are at different times, they can relate the values to the sound levels in those locations. This recording feature allows students to carry the device around and record sound levels, and then export the results all as one file. The default settings give 10 samples per second, all of which are output to this file. A science teacher would complain about the inappropriate number of significant figures given in the dB values, so students should be warned of this. When the file is opened it is a text file with data in the format: "2012:02:21 05:46:41.044 average: 50.326469, peak: 50.326469" providing the date, time, and average and peak dB values.
#DECIBEL APP ZIP#
This gives the option to email the values recorded in the current session as a zip file. You can output data from the app using the arrow icon at the top right. It also shows a graph of recent values - these are the sound level values (not a graph of the sound waveform). One feature that I like is that at the top it gives in words a typical comparison - e.g. The meter scale shows values above 75 dB as red, and has a total range from 0 to 110 dB. In the centre is an analog meter format visual display. At the bottom of the screen it gives both the current dB level (in the centre), a recent peak value (to the right) and a maximum value recorded during the current session (on the left). I show a typical screen from the app here.
0 kommentar(er)
