Digital Processing of Audio Signals

Prasanna Vemuri

Padma Parakala

Rekha Vemuri

Presentation Outline

• Objective• Product Idea• Development strategy• Design Phase• Alternate Approach• Cost Analysis• Time line• Conclusions

Objective

• The main objective of this project is to design an audio amplifier and to process the output signal using digital filtering techniques

Product Idea???

What can be done to reduce noise?

Which process is more suitable?

Product Idea???

What are the resources available to achieve the task?

• Is the product idea feasible and within the economical constraints?

Development Strategy

Design Phase

Analog Audio Amplifier

Analog to Digital Conversion

ADH 0

From Output of Audio Amplifier

NI BNC 2120 DAQ Board

Digital Filtering

Digital to Analog Conversion

DAC 0

To Speaker

NI BNC 2120 DAQ Board

Speaker

Limitations

• Hissing --- Lack of Precision equipment

• Time lag – Scan time for acquiring and processing the data

Alternate Approach

FIR Filter

Alternate Approach Contd..

• To eliminate time lag

-- Using scan clock

-- Using case structure

• To eliminate hissing

-- IIR Filter with Scaled Window

Cost AnalysisPart Description Cost ($)

U1 LM386 Audio Power Amplifier Chip 0.55

R1 10 Resistor 0.15

C1 220f Electrolytic Capacitor 0.15

R2 1k Resistor 0.15

C2 10f Electrolytic Capacitor 0.10

R3 10k Resistor 0.15

Bypass 100pf Ceramic Capacitor 0.10

R4 10 Resistor 0.15

C4 0.05f Ceramic Capacitor 0.10

C3 220f Electrolytic Capacitor 0.15

E3631A Triple Out DC Power Supply, HPIB/RS-232 1,122.00

BN2120 E-Series Multifunctional I/O DAQ 395.00

TOTAL 1518.75

Time Line

Conclusions

• Real time application of digital filtering is more efficient for the acquisitions at lower speeds

• Waveform graph after filtering showed reduction in noise of the audio signal

For more information

Visit us at:

www.cas.unt.edu/~prasanna/ELET5330