Sound Ecology and Acoustic Health, Part 1: Developing a basic Android Application

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Circuit Cellar, Kick Media Corporation, U. S. A.
Introduction to periodical article: A background level of urban noise is, unfortunately, one of those inconveniences that we must put up with to live in a community. You and your neighbour can sympathize with each other at a BBQ about being awakened by the dawn chorus of birds or early morning commuter traffic noise. You can band together to solve that problem with a joint big win on the local lottery and buy new houses elsewhere. Sometimes, the noise can be such an issue across a wide community that even federal politicians can be stirred from their comfortable seat to assist in the investigation as in the case of the Windsor Hum (2009 - 2014, However, as mentioned in our urban noise article Circuit Cellar issues, the BBQ conversation might go along these lines. You say “That noise at 2 a.m. every night last week, hasn’t it been driving you crazy?” and your neighbour responds “What noise?” After such a conversation, it is worthwhile getting your hearing tested. There are conditions affecting the ears, such as Tinnitus or “ringing in the ears”, which could be alleviated with professional help. However, with that issue ruled out, you now have a noise in your house that nobody else in your neighborhood seems to have. It’s time to become a noise detective. There are apps to record your prowess in “singing in the shower” and those, to a limited degree, would be useful in capturing the noise. If your neighbour agrees, check at their house or in their garden. Everybody’s hearing is different and there’s a possibility that the noise you are hearing is there and they are just not sensitive to it. Recording is good - it confirms that something physical is present in several locations. However we want a little more than that. We have been working with local Acoustics firms who have suggested that people should look out for “home resonances” as playing a role in noise nuisances you hear and your neighbour does not. We have all seen neighbourhood kids playing with resonances - tiny, gentle kicks of their legs at just the right time can cause a playground swing to reach great heights. In a similar way, parts of your house - wall, basement concrete pad, or heating duct - can be constructed in such a way that they sympathetically vibrate with, and amplify, some tiny, gentle, totally insignificant incoming vibration through the air or ground. To analyze the frequency response of your house including resonances we need a “recording app” with a number of custom DSP extensions for resonance identification. Rather than undergoing the hassle of trying to gain access to - and then modify - the source code of an existing app, we took a more pragmatic approach. If the local teenagers can build their own Android apps, surely we can too! To build our own recording app, we would customize from online Android tutorials ( Fig. 1A outlines our plan for our first Android activity built without any teenage assistance necessary. When this WAT_AN_APP is finished we will be able to record and playback an audio .3GPP file using a modified Android MediaRecorder app and be able to better show to others that the noise problem we hear physically exists. However we also want to be able to use our own DSP experience from work to add any special analysis feature. In future articles we will look at using a different Android activity approach that allows us to capture sound into an uncompressed data buffer. Fig. 1B demonstrates that goal of using some DSP “spectral” analysis to identify an unwelcome “spectral” presence, a ghost. We extend the app to do more sophisticated analysis that uses graphics to display the presence of home resonances that might be impacting the acoustic health of your home.
Sound Ecology, Acoustic Health, Android Application, Signal processing
Adrien Gaspard, Mike Smith and Nicholas Lepine , "Sound Ecology and Acoustic Health, Part 1 Developing a basic Android Application", Circuit Cellar, Issue 300, pp 16 - 26, July 2015, Kick Media Corporation, U. S. A.