This document discusses audio signal processing. It begins with an introduction to analog and digital audio signals and their frequencies. It then covers analog to digital conversion, various audio effects and processing techniques like compression, echo cancellation, filtering, and equalization. Finally, it discusses digital to analog conversion and concludes with advancements in digital audio technology.

1. AUDIO SIGNAL
PROCESSING
DONE BY
SANJAY.K
SARAN.S
SOMANSANKARA.P.R
VISHNUPRASANTH.B

2. AGENDA:
• INTRODUCTION
• ANALOG TO DIGITAL
CONVERSION
• AUDIO EFFECTS
• DIGITAL TO ANALOG
CONVERSION
• CONCLUSION

3. INTRODUCTION
Audio Signal processing is a method where intensive algorithms, techniques are applied
to audio signals. Audio signals are the representation of sound, which is in the form of
digital and analog signals. Their frequencies range between 20 to 20,000 Hz, and this is
the lower and upper limit of our ears. Analog signals occur in electrical signals, while
digital signals occur in binary representations. This process encompasses removing
unwanted noise and balancing the time-frequency ranges by converting digital and
analog signals. It focuses on computational methods for altering the sounds. It removes
or minimizes the overmodulation, echo, unwanted noise by applying various techniques
into it.

4. ANALOG TO DIGITAL CONVERSION
Analog audio signals are more likely to be influenced by noise and distortion.
Converting them into digital signals allows convenient manipulation, storage, and
transmission without any quality degradation. It uses a specified sampling rate and
converts the electric signals into the binary bits resolution. The higher the sampling rate
and precision measurements, the higher the quality.
The performance of ADC is defined by its bandwidth and signal-to-noise ratio (SNR).
Bandwidth is characterized by sampling rate, and SNR differs when there is a change in
resolution, accuracy, aliasing (occurs when encoded signal is different from the original
signal), etc. ADC is considered in its ideal state when SNR of ADC

5. AUDIO EFFECTS-AUDIO PROCESSING
TECHNIQUES
Post-processing algorithms are used to suppress the noise and any artifacts created in
the first stage of processing. It is primarily focused on echo, distortion removal, and
speech enhancement. Equalization and filtering are popular post-processing techniques
to add reverberation and noise control.

6. PROCESS INVOLVED
IN AUDIO TECHNIQUES
• DATA COMPRESSION
• AUTOMATIC ECHO CANCELLATION(AEC)
• FILTERING
• EQUALIZATION

7. DATA COMPRESSION
Compression is one of the most powerful mixing tools which is a process to reduce the
dynamic range of audio signals. Dynamic range is the difference between the highest and
lowest range of an audio signal.
For example, while screaming or whispering pitch is either too high or too low and, in this
case, if we record it without compression, then the resulting sound will be distorted. The
compressor fixes this problem by attenuating the loudest sound and boosting the slowest
sound. It helps us find the perfect balance of audio track and gives us more natural sound
without distortion. It also reduces the bandwidth of digital audio streams and storage size of
the file to save storage space and faster transmission.

8. DATA COMPRESSION

9. AUTOMATIC ECHO CANCELLATION(AEC)
Acoustic Echo Canceller plays an important role in audio signal
processing. It removes the echo, reverberation and unwanted noise
caused by acoustic coupling between the microphone and loudspeaker.
Microphones capture the far-end speech due to the acoustic coupling.

10. FILTERING
Filters are considered the most basic circuit in any signal processing used in almost
every process. It removes the unwanted noise, echo, distortion, and allows the filtered
data to pass through it. We will be discussing pass filters that allow only specific
frequencies while rejecting others.

11. FILTERING
Low-pass filter
Low-pass filters allow the frequencies below the
selected cut-off frequency level and cut the
frequencies above the cut-off range.
• High-pass filter
A high-pass filter is the opposite of a low-pass filter.
It filters and passes the frequency, which is higher
than the cut-off frequency range and attenuates the
frequency lower than the cut-off range.

12. FILTERING
• Band pass filter
• After resampling of signals, band pass filter is applied to remove the extra noise and
be considered the most ideal filter in signal processing. It attenuates the frequencies
which are higher or lower than the cut off frequencies range and only passes the
frequencies which fall within the cut-off range.

13. FILTERING
• Band-rejection/stop filter
It is also known as a notch filter and opposite of band-pass filter. It leaves most of the
frequencies unaltered and attenuates those within a specified range to very low levels.

14. EQUALIZATION
Equalizers are used to alter or adjust the frequency so that the sound spectrum
frequency at the transmitter should match the sound spectrum’s frequency at the
receiver. Frequency ranges are being adjusted to high or low using low-pass
filter, high-pass filter, band-pass filter. It removes the delay between different
frequency components and gets the desired output.

15. DIGITAL TO ANALOG CONVERSION
Modern audio signals are mostly found in digital forms like MP3 but, if you want to listen
to it through the speaker, it needs to be converted in analog form. It transforms digital
data streams into analog audio signals, and then the converted analog signals are sent
to amplifier. It is then used by the output devices like speakers, music players. This
process improves the overall sound quality and enhances the listening experience.
Some of the DAC enabled devices are digital speakers, CD players, music players, etc

16. CONCLUSION
Advancements in digital audio technology have propelled us to have very efficient and
high-quality speech processing algorithms in place. These algorithms are applied in the
process of recording, storing, and transmitting the audio content.