Decibel 10

Decibel 10 by SkyPaw Ltd. is a well crafted and free app to measure sound levels in decibels.  While this is certainly not the only sound level app, in my opinion it is the best. It has a beautiful and intuitive interface, making it simple enough for even elementary students to easily measure sound levels.  The app provides convenient comparison for the values obtained with short word descriptions for situations that typically have that sound level. The ability to record and export (e.g. as email attachment) the decibel values along with time information is a significant strength. With this app and a speaker system it would be easy for a museum to make an interactive display for users to become familiar with decibel readings.

I show a typical screen from the app here.  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).  In the centre is an analog meter format visual display.  The meter scale shows values above 75 dB as red, and has a total range from 0 to 110 dB. One feature that I like is that at the top it gives in words a typical comparison - e.g. "average quiet home".  It also shows a graph of recent values - these are the sound level values (not a graph of the sound waveform).

You can output data from the app using the arrow icon at the top right.  This gives the option to email the values recorded in the current session as a zip file.  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.  A science teacher would complain about the inappropriate number of significant figures given in the dB values, so students should be warned of this.  The default settings give 10 samples per second, all of which are output to this file.

This recording feature allows students to carry the device around and record sound levels, and then export the results all as one file.  If the students note where they are at different times, they can relate the values to the sound levels in those locations.  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.  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.

A bit of background on decibels (dB).  The decibel is used to compare two power levels, with the dB difference being 10 times the logarithm of the ratio of the powers.  More specifically we use dB in sound to compare the sound intensity values (W/m²).  For example if one sound level was 1000 times another, that would be a 30 dB difference. With sound it is conventional to establish a reference level of 0 dB at an intensity of 1.0x10^-12 W/m², the approximate limit of human hearing. Decibels are named in honour of scientists, engineer and inventor Alexander Graham Bell (1847-1922).  Although born in Scotland, he emigrated to Canada at age 23.  Although he has a long list of inventions, he is best known as the inventor of the telephone.  A museum in his honour is in Cape Breton Island in Nova Scotia. An interesting tidbit: he was born without a middle name, and so wanted one that he was given a middle name for his eleventh birthday (named after a well liked Canadian staying in their home).

The app is developed by SkyPaw Ltd., which also produce apps for timers, seismometers, a calculator and a metronome, among others.

My overall rating: 9 (out of 10).  I think that the app is near perfect, and particularly for a free app, is impressive.  I would like to see a more appropriate numbers of significant figures in the dB output in the export file, and if it were possible to somehow include annotations that would be exported with the file that would be great. So whether you want to have your students explore noise pollution, provide evidence to your apartment neighbours that they are too loud, or convince your spouse or children that they have the stereo or television too loud, this is a fun and useful app.  A few of those commenting on the app store report issues with the iPhone 4s that I have not been able to check. It certainly has worked flawlessly for me on an iPad 2 running the most recent iOS.  According to the developer it runs on iPad, iPhone and iPod touch, requiring iOS 3.2 or later.