UMass Amherst SDP06

Draft System Specification

Principle of Operation:

The user will enter the location or the angle at which the desired individual is, then using the eight microphones and an eight channel analog to digital converter, delaying the signal at each microphone accordingly, the signal is fed into the computer and after certain manipulations the voice of the desired individual is heard through the speakers at the computer.

The user also has the option to use an electronic bug. The bug is utilized to track a certain target on which it is installed. The bug will generate a signal with a frequency much higher than that of human voice. This signal is detected by the SVTS and is used to locate the target. The user will be able to listen to/record the voice signals coming from the target’s position.

Input:

There are two modes of operation for the SVTS, Mode One and Mode Two. Mode one requires the user to specify a direction to which the user intends to listen. The location will be specified by measuring the amount of degrees the desired location is away from the axis along the array of microphones. Mode Two of operation will allow the user to bug an individual. Once the bug is installed, the SVTS will be able to detect and listen to the person.

In Mode One, the user will input the desired location through the user interface. A program such a Visual Basic will provide the user with the appropriate prompts. If an invalid angle (i.e. any angle outside 0o-180o range) is entered the user will be notified and told to try again. Once the desired location is specified, the eight microphones aligned in an array will pick up voice signals. The voice signals received by each microphone will be amplified and inputted into an eight channel A/D converter. The inputted signals will fall in between the frequency range of 20 Hz to 20 KHz, and the A/D converter must be able to sample at least twice this frequency. The A/D converter will be synchronized with MATLAB. MATLAB then performs the necessary calculations to apply the proper signal delays to the signal received by each microphone. The amount of delay required will be different for each channel depending upon the geometry of the location.

In Mode Two of operation, the bug placed on an individual will be emitting a signal with frequency of roughly 30 kHz, which is above the audible range of humans. The SVTS will then scan the surrounding area until it finds a location where a frequency of 30 kHz is located. Once this frequency is detected the SVTS will track the bug around the room. By locating where the 30 kHz signal is being emitted from the proper delay signals can be added accordingly.

Output:

The output will be an audio signal sent to a set of speakers in range of the user. The audio signal will be the summation of eight synchronized individual microphone signals. The audio signals are able to be added by applying the appropriate signal delay to each channel through MATLAB. When the SVTS is in Mode Two of operation, a low pass filter will be applied to only allow frequencies of 20 Hz to 20 KHz to be outputted through the speakers.

Specification of the Block Diagram:

The blocks seen in the system block diagram are described below as:

Array of Microphones:

There are eight omni directional microphones to help receive the sound signals effectively. These microphones are chosen and placed using beam forming.

Amplifier Stages:

The sound signals that are captured by the microphones are very weak and cannot be directly fed into the A/D converter for processing, so we need amplifier stages between the microphones and A/D converter, so that we can amplify the signal levels to the optimum level and fed into A/D converter for processing.

A/D Converter:

The eight channel analog to digital converter converts the analog signal coming from the microphones into a digital sequence and then it is fed into the computer and the resulting sequence is manipulated using Matlab data acquisition toolbox.

Each channel in the A/D converter gets the input signal from a different microphone.

Matlab Data Acquisition Toolbox:

When the sample sequence from A/D converter is fed into the computer, the proper delay that needs to be gives to each sequence from the microphones is predetermined for an angle and proper delays are given to the signals and they are added constructively and then the resulting output is heard from the speakers connected to the computer. The ideal output that is heard from the speakers is the sound that is selectively chosen using the eight omni directional microphones.

User Interface:

The user interface consists of a computer monitor, keyboard and speakers. The input location or the angle of the desired individual is entered through the keyboard, which can be seen on the computer monitor, and the individual’s voice is heard through the speakers connected to the computer.

Home	Draft System Specification Principle of Operation: The user will enter the location or the angle at which the desired individual is, then using the eight microphones and an eight channel analog to digital converter, delaying the signal at each microphone accordingly, the signal is fed into the computer and after certain manipulations the voice of the desired individual is heard through the speakers at the computer. The user also has the option to use an electronic bug. The bug is utilized to track a certain target on which it is installed. The bug will generate a signal with a frequency much higher than that of human voice. This signal is detected by the SVTS and is used to locate the target. The user will be able to listen to/record the voice signals coming from the target’s position. Input: There are two modes of operation for the SVTS, Mode One and Mode Two. Mode one requires the user to specify a direction to which the user intends to listen. The location will be specified by measuring the amount of degrees the desired location is away from the axis along the array of microphones. Mode Two of operation will allow the user to bug an individual. Once the bug is installed, the SVTS will be able to detect and listen to the person. In Mode One, the user will input the desired location through the user interface. A program such a Visual Basic will provide the user with the appropriate prompts. If an invalid angle (i.e. any angle outside 0o-180o range) is entered the user will be notified and told to try again. Once the desired location is specified, the eight microphones aligned in an array will pick up voice signals. The voice signals received by each microphone will be amplified and inputted into an eight channel A/D converter. The inputted signals will fall in between the frequency range of 20 Hz to 20 KHz, and the A/D converter must be able to sample at least twice this frequency. The A/D converter will be synchronized with MATLAB. MATLAB then performs the necessary calculations to apply the proper signal delays to the signal received by each microphone. The amount of delay required will be different for each channel depending upon the geometry of the location. In Mode Two of operation, the bug placed on an individual will be emitting a signal with frequency of roughly 30 kHz, which is above the audible range of humans. The SVTS will then scan the surrounding area until it finds a location where a frequency of 30 kHz is located. Once this frequency is detected the SVTS will track the bug around the room. By locating where the 30 kHz signal is being emitted from the proper delay signals can be added accordingly. Output: The output will be an audio signal sent to a set of speakers in range of the user. The audio signal will be the summation of eight synchronized individual microphone signals. The audio signals are able to be added by applying the appropriate signal delay to each channel through MATLAB. When the SVTS is in Mode Two of operation, a low pass filter will be applied to only allow frequencies of 20 Hz to 20 KHz to be outputted through the speakers. Specification of the Block Diagram: The blocks seen in the system block diagram are described below as: Array of Microphones: There are eight omni directional microphones to help receive the sound signals effectively. These microphones are chosen and placed using beam forming. Amplifier Stages: The sound signals that are captured by the microphones are very weak and cannot be directly fed into the A/D converter for processing, so we need amplifier stages between the microphones and A/D converter, so that we can amplify the signal levels to the optimum level and fed into A/D converter for processing. A/D Converter: The eight channel analog to digital converter converts the analog signal coming from the microphones into a digital sequence and then it is fed into the computer and the resulting sequence is manipulated using Matlab data acquisition toolbox. Each channel in the A/D converter gets the input signal from a different microphone. Matlab Data Acquisition Toolbox: When the sample sequence from A/D converter is fed into the computer, the proper delay that needs to be gives to each sequence from the microphones is predetermined for an angle and proper delays are given to the signals and they are added constructively and then the resulting output is heard from the speakers connected to the computer. The ideal output that is heard from the speakers is the sound that is selectively chosen using the eight omni directional microphones. User Interface: The user interface consists of a computer monitor, keyboard and speakers. The input location or the angle of the desired individual is entered through the keyboard, which can be seen on the computer monitor, and the individual’s voice is heard through the speakers connected to the computer.
Statement of the Problem
Requirements Specification
System Block Diagram
Draft System Specification
Preliminary Design Review
MDR Specifications
Project Update - 2nd Feb 2006 NEW
UMass Amherst
College of Engineering
ECE
SDP06

Selective Voice Tapping System (SVTS)

Draft System Specification

Principle of Operation: