Construction Of A Digital Voice Recorder

Project and Seminar Material For Electrical Electronics Engineering EEE

Project and Seminar Material For Electrical Electronics Engineering EEE


Abstract


In the world today, the need to keep record of information and other messages is very relevant so as to retain authenticity of such information. No doubt everyone as experienced the frustrations of forgetting thoughts, ideas and facts which can lead to embarrassing situation or time consuming resolutions.

Over the years, audio has always been stored in a cassette tape in analog format but due to the fact that a cassette tape’s magnetic particles lose their charge, causing the quality of the original recording to deteriorate. Also, recording in analog format in cassette tapes is prone to error due to noise and lacks the ability of further processing over the computer.

The introduction of digital recording technology has solved a lot of problems encountered while using the cassette tape [analog]. The development of a digital voice recorder is the solution. It is used for recording of audio in digital mode.

This project describes the applications and the use of the digital for digital recording. It went further to analyzing the construction techniques applied towards achieving an effective device [DVR] for the purpose of quality recording in digital mode.


Table Of Content


Preliminary Page(s)

  • Title Page
  • Approval Page
  • Dedication
  • Acknowledgement
  • Abstract
  • Table Of Content

Chapter One

  • Introduction

Chapter Two

  • Literature Review

Chapter Three

  • Methodology

Chapter Four

  • Result Analysis

Chapter Five

  • Conclusion And Recommendation
  • References

Chapter One


Introduction

Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, or sound effects. The two main classes of sound recording technology are analog recording and digital recording.

Analog recording is achieved by a small microphone diaphragm that can detect changes in atmospheric pressure (sound waves) and record them as a graphic representation of the sound waves on a medium such as a phonograph (in which a stylus senses grooves on a record).

In magnetic tape recording, the sound waves vibrate the microphone diaphragm and are converted into a varying electric current, which is then converted to a varying magnetic field by an electromagnet, which makes a representation of the sound as magnetized areas on a plastic tape with a magnetic coating on it. Analog sound reproduction is the reverse process, with a bigger loudspeaker diaphragm causing changes to atmospheric pressure to form acoustic sound waves.

Digital recording and reproduction converts the analog sound signal picked up by the microphone to a digital form by a process of digitization, allowing it to be stored and transmitted by a wider variety of media. Digital recording stores audio as a series of binary numbers representing samples of the amplitude of the audio signal at equal time intervals, at a sample rate so fast that the human ear perceives the result as continuous sound.

Digital recordings are considered higher quality than analog recordings not necessarily because they have higher fidelity (wider frequency response or dynamic range), but because the digital format can prevent much loss of quality found in analog recording due to noise and electromagnetic interference in playback, and mechanical deterioration or damage to the storage medium. A digital audio signal must be reconverted to analog form during playback before it is applied to a loudspeaker or earphones.

Terms In Digital Voice Recording

Word Size

The number of bits used to represent a single audio wave (the word size) directly affects the achievable noise level of a signal recorded with added dither, or the distortion of an undithered signal. Increasing a sample’s word length by one bit doubles its possible values, likewise increasing the potential accuracy of each sample and the fidelity of the recording to the original. 24-bit recording is generally considered a current practical limit as this word length allows a signal-to-noise ratio exceeding that of most analog circuitry, which by necessity must be used in at least two points in the recording/playback chain.

Sample rate

The sampling rate, sample rate, or sampling frequency defines the number of samples per second (or per other unit) taken from a continuous signal to make a discrete signal. For time-domain signals, the unit for sampling rate is s-1. The inverse of the sampling frequency is the sampling period or sampling interval, which is the time between samples.

This material contains electrical diagrams, circuits, illustrations and more (Very detailed)


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