Physical System

 

 

Individual Components

 

Dbx RTA microphone

 

Omni-directional Measurement Microphone

Element: Back Electret Condenser

 Frequency: 20 Hz - 20 kHz

 Impedance: 250 30% (at 1,000Hz)

Sensitivity: -63 dB 3 dB ( 0 dB=1V/ microbar  1,000 Hz indicated by open circuit )

 Operating Voltage: Phantom power 15V D.C.

We use four of these microphones in the configuration explained in the Project Overview Section. The microphones are mounted onto to robotic modules designed to move the microphones along a linear pathway. The microphones listen for a sound produced programmatically from our sound output generation interface and played on a standard computer speaker. The signals output by the microphones is amplified and fed into the Data Acquisition Device (DAQ).

 

D.A.Q. 

 

The data acquisition system (DAQ) that is used for the acoustic sensing device is the National Instruments NI USB-6210:

16 analog inputs (16-bit, 400 kSamples/s)

The maximum sampling rate is 400 kSamples/s aggregate.

 

The DAQ receives the amplified microphone signals and transforms them for use in a computer system, in particular, our LabVIEW software interface for further processing and analysis. The DAQ is capable of 400,000 samples/second aggregate sampling frequency; but, because we use four DAQ input channels simultaneously each channel can be sampled up to 100,000 samples/second.

 

Robotic details

The robots were built by Chase LaFont using Lego MindStorm Kits.

 

 

 

 

 

 

 

Each robot holds one pair of microphones in fixed positions which hold the distance between the two microphones constant. The robots move on three wheels. Two wheels are driven by Lego MindStorm servomotors and the third wheel provides stability and moves passively.

 

Lego MindStorm   Servomotor

 

 

These servomotors are controlled by a microcontroller which is given instructions from the LabVIEW interface via a USB connection with the computer. The instructions are originate from the adaptive movement algorithm in LabVIEW

 

NXT ARM7: A Lego MindStorm Microcontroller programmed within LabVIEW using a specialized toolbox.