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West Virginia University – LCSEE Senior Design 480/481Group 01 – The Cloud-Based Laser Microphone

GROUP LEADER: ANIRUDH RAWAT (EE) ADVISORS: DR. ALAN BRISTOWGROUP MEMBERS: BASIL DIXON (EE) || BRYANT DONATO (CPE) || ALI SULTAN (EE) MENTOR: DR. DARYL REYNOLDS

OVERVIEWGroup 1 has designed and built a laser based audio surveillance system that effectively captures and records ambient audio via a laser beam reflecting off of a smooth, reflective surface, and stores it in the cloud. The system consists of two platforms:

1. The hardware platform which collects and amplifies audio using a laser, chiefly via the Laser Acquisition and Signal Processor (LASP).

2. The software platform, which consists of a commercial Windows PC, or Raspberry Pi running Linux. The Linux platform has a pre-programed script that records audio and securely transmits it to the cloud.

SIGNAL ACQUISITION (HARDWARE)

The hardware platform’s flagship unit is the LASP. The LASP consists of a power efficient LM386 based audio amplifier circuit that is fed via a NPN phototransistor. The LASP is self contained and grounded in an aluminum enclosure that acts as a Faraday cage, and outputs audio using a standard 3.5mm audio jack. Battery life using a standard 9V battery is over 2 days.

SOFTWARE PLATFORM

FFT OF A CAPTURED SIGNAL

TESTING PROTOCOL

WARNINGWARNING 

THE CBLM WAS CONSTRUCTED FOR RESEARCH PURPOSES ONLY UNDER UNIVERSITY GUIDELINES. IT IS NOT FOR

CASUAL CIVILLIAN USE. IN ADDITION, LASER RADIATION IS HARMFUL TO THE EYE, AND CAUTION SHOULD BE USED

WHEN OPERATING THE LASER. YOU ARE RESPONSIBLE FOR FOLLOWING ALL FEDERAL, STATE, AND LOCAL LAWS WHEN

UTILIZING THE CBLM FOR LEGAL PURPOSES ONLY!

• The software platform consists of:

• RaspberryPi running Linux & Windows PC

• Cloud Storage Server w/ Database

• Cloud storage server can e hosted on Amazon’s Elastic Computing Cloud (EC2)

• EC2 can set up multiple operating systems or databases according to the users needs in a matter of seconds!

• An automation script securely transfers files to EC2

• You may also skip the software platform and use headphones to listen to audio in real time.

A structured and tough testing protocol was established to investigate the effectiveness of the CBLM Prototype. The CBLM passed the majority of our tests, but some concerns are outlined below:

• Testing on multiple surfaces: Glass windows of varying thickness, double paned glass, and damped glass• Double paned glass can significantly reduce audio quality

and diminish effectiveness due to multiple refraction.

• Glass with a soft, sound absorbing surface behind it like a notice board can damp sound

• Ambient light effects• Indoor lights present a noticeable 60Hz humming sound• Outdoor testing was not performed at this time, but will

have similar effects such as adding white noise to the signal• Can be mitigated with aggressive signal processing.