Additional detection of sound?

[mwaters]

If you want one, I'd get the 1D unless you live in areas like Central California or Japan.

I appreciate the advice! Looks like I can get what I need for $160. I am quite comfortable with putting that in a similar case I have, and whatever necessary wiring, soldering, and mechanical work etc.

But I have other priorities at present.

[mwaters]

I have the InfraSound Detector app installed on my Android tablet. I've never used it, but now I'm going to play with it some.

• InfraSound Detector allows you to detect infrasound signals below 20 Hz.
  
• InfraSound Detector is the App that allows you to detect infrasound (infrasonic) acoustic signals below the user-defined frequency (up to 30 Hz by default).
  
• Infrasound propagates hundreds of miles and can penetrate walls, mountains and other obstacles without loss.
  

This detector can be useful in following cases:

• To find out any suspicious low frequency noise, vibrations, and sounds in building structures.
  
• To register a number of hazardous atmospheric phenomena, including aircraft wake vortices, clear air turbulence, severe thunderstorms and tornadoes as well as any seismic events and volcano activities. As a benefit, it allows early detection of tornadoes from hundreds of miles away.
  
• To detect underground activity, e.g., tunnel digging.
  
• To detect some kind of infrasonic weapons, that cause physical pain without human detection.
  
• To check out the quality of bass sounds (low frequency) of your subwoofer speaker system as well as any loudspeakers.
  

Result of detection can be shown on the screen in the foreground mode and also be presented in the notification form and (or) by sound (vibration) in the background mode when the screen of the Android device is turned off. All events can be recorded in the log for later analysis. The lower working frequency is depend on the audio specification of the current Android device and can be reached as low as 4 Hz. For better result, the high quality Android device with internal microphone should be used to determine the infrasound signal, but sensitivity on the lowest frequencies will be worse anyway. Also, you can use a special external infrasound microphone connected to the audio jack (microphone input of the ear plug connector).

The idea of the App is based on the fact that any analog system (microphone and amplifier of your Android device in this case) does NOT have ideal characteristics and infrasound signals can be infiltrate through it down to 4 Hz.

Features:

• Completely NO ads.
  
• The signal level indication.
  
• Vibration indication of the alarm event.
  
• Event log is recorded automatically. Signal spectrum and location information can be included in the log.
  
• The converter infrasonic signals into audible sounds. So you can hear infrasonic signals.
  
• Background mode with notifications. Once this option starts, the App runs quietly in the background and requires no human interaction until the alarm event happens. It continues to run even after the device reboots.
  
• Adjustable battery consumption in the background mode. The App is designed to conserve your device battery and allows to select the data update rate. The more update rate time, the less battery it takes.
  
• Comprehensive spectrum analysis with different ways to display results: spectrum, waterfall, oscilloscope.
  
• Adjustable frequency range and selectable frequency resolution between 0.1 and 1 Hz.
  

[SJ Clay]

I am interested from an infrasound perspective of correlating lightening strikes and thunder. Where can I get additional historic information on individual strikes (i.e. Intensity, duration, ...).

Thanks
Scott

[mwaters]

I am interested from an infrasound perspective of correlating lightening strikes and thunder. ...

See the links in post #2 above. They show that it is not practical.

[SJ Clay]

Thanks Mike,

I had seen that, dated and not really the case.

There are a number of papers that have been published on infrasound, thunder, lightening and sprites. Working in the Infrasound community I have seen signals, on infrasound arrays, with characteristics similar to those reported.  I have just started looking to gathering information about recent thunderstorms in my region and I am looking for any databases with time, lat/lon, and any other information that might be reported. 

Thanks,

Scott

[mwaters]

Okay, it sounds like you are talking about Infrasound as a stand-alone method of detection. A few questions come to mind.

1. Is this method actually in use anywhere?
   
2. What is the range of such a detection method?
   
3. What is the approximate accuracy?
   
4. Strong winds can blow sound waves around. That being the case, how is that compensated for?
   
5. What station density is required for this?
   

[SJ Clay]

Yes using Infrasound Arrays and characterizing the detected signals.

1. There are a number of arrays spread out across the country.  Some are part of our nuclear monitoring (CTBTO), some monitoring Volcanos, and still others for research.
2. It depends on the source strength, weather and propagation frequencies.  With the right atmosphere, a small explosive source can be detected from several hundreds of kilometers. Strong winds blowing the source signal away from the receiver can make that signal undetectable. 
3. Accuracy is an interesting question, infrasound propagation is as you can imagine directly affected by the atmosphere. So how do you quantify accuracy, you should or should not see signal based on what? Infrasound modeling is a developing science, so in short as a community we see a lot, and often we can explain why we see or don't see signals. 
4. The folks looking at Tornados using infrasound face that problem.  in this case you need to have your arrays upstream of the weather front and determine the density of arrays necessary to do that detection. 
5. An adequate array will having at least five elements (elements one in the center, with the other four elements to the north, East, South and West) with at least 50m between elements. That is suitable for monitoring the signals that most infrasound sources produce.

[mwaters]

Thank you, Scott.