Signal Processing Commons^™

Design Of Hardware To Aid Smartphone-Based Oscilloscope App, Riddock Moran

Honors Theses

A smartphone-based oscilloscope improves on traditional lab oscilloscopes in accessibility and portability but faces several performance limitations compared to traditional oscilloscopes. Among these, an oscilloscope app that uses the phone’s audio to read voltage signals will have a sampling rate and voltage bottlenecked by the capabilities of the audio codec, which will rarely exceed a rate of 48 kHz and 1 volt, respectively. Additionally, smartphones lack the ability to read line-in audio, allowing only one channel input through the microphone. Direct connections to an audio source may not be possible due to requiring an audio jack connection, and different poles …

Analog & Digital Remote Synthesizer, Adam Brunner, Andrew Cihon-Scott, Scott Grisso, Linus Wright

Williams Honors College, Honors Research Projects

The purpose of this project is to develop and design an analog synthesizer musical instrument that integrates embedded digital hardware into the design to enable control from a remote source. The use of digital hardware enables the potential for a wide range of convenient features such as sound profile saving and loading, output recording functionality, and the ability to accept digital input from another musical instrument utilizing the Musical Instrument Digital Interface (MIDI). In addition to the synthesizer itself, this project also includes the design of a companion application that can be hosted on a wide variety of consumer computing …

Methods Of High-Fidelity, High-Efficiency Class-D Audio Amplification, Kaleb Kassaw

Electrical Engineering Undergraduate Honors Theses

Gallium nitride-based field effect transistors (FETs) have opened a path for full-frequency-range class-D audio amplifiers with low distortion and noise, thanks to their ability to switch at much higher frequencies than that of the upper range of human hearing. Compared to traditional silicon-based transistors, GaN-based transistors offer superior efficiencies, particularly at power levels below their maxima. Paired with an analog-to-digital converter, digital signal processor, and pulse-code modulation to pulse-width modulation converter, these transistors are used to design and implement a solid-state amplifier capable of generating 100 watts of output through speakers with an impedance of 8 ohms using a 1-volt …

Pseudo-Stereo Audio Processor, Zachariah David Bunce

Electrical Engineering

Due to both technical and resource limitations, non-professional audio production must often record with a single microphone, creating a mono audio signal. Even some originally multi-channel audio files often combine the separate channels into a single channel to save memory. However, this channel limitation makes any music held within the audio duller during listening. The Pseudo-Stereo Audio Processor remedies this situation, introducing a quadrature phase shift onto a given single-channel audio signal, producing multiple phase shifted output signals. These separate fixed-phase output signals are then recombined to produce a variable phase difference, emulated two-channel version of the input signal, allowing …

Dynamic Voltage Rail Audio Amplifier, Evan Von Duhn, Timothy Oshatiouk, Slavisa Tosanovic, Andrew Cantrell

Williams Honors College, Honors Research Projects

The goal of this project is to create a high-quality, power-efficient audio amplifier. Most modern audio amplifiers use a constant amount of power regardless of the signal that is being amplified. This means that both loud and quiet portions of the audio signal require the same amount of power to amplify. The idea for this high-quality, power-efficient audio amplifier is that the quieter portions of the audio signal can be amplified using less power. This will be achieved by first analyzing the audio signal and controlling the power source based on the signal’s needs. Therefore, louder parts of the audio …

Analysis And Simulation Of Convolution Reverb Using City Tech’S New Auditorium, Tian Leng

Publications and Research

In digital signal processing, convolution reverb can simulate the reverberation of a real acoustic space. The acoustics of different seating areas in an auditorium can vary from each other. To determine the reverberant characteristics of City Tech new building’s auditorium, impulse response (IR) signals are recorded in five key locations of the auditorium.

Directly recorded balloon burst is chosen as the source of impulse source. An omnidirectional and a cardioid microphone with flat frequency response curves are used to record IR signals to 24-bit monophonic wav files. Each IR signal, along with a vocal, is convoluted in MATLAB through both …

Portable High-Definition Audio Spectrum Analyzer, Alex Zahn, Jamie Corr

Electrical Engineering

The Portable High-definition Audio Spectrum Analyzer (PHASA) allows the user to visualize the audio frequency spectrum of an incoming line-level stereo audio signal. Upon pressing the touch screen spectrum graph, the PHASA displays the corresponding frequency and volume levels as well as crosshairs at the touched location. The PHASA features multiple left/right channel display modes— Left channel only, right channel only, both channels simultaneously, and the average between the two channels. The PHASA features multiple resolution display modes (standard-resolution and high-resolution) and multiple dynamics display modes (standard dynamics, averaging, and peak/hold). The PHASA accepts input audio via a 1/4" TRS …

Dual Method Headphone Amplifier, Joseph S. Gross, Timothy P. Murphy

Electrical Engineering

Many high impedance headphones underperform their full potential when directly connected to the audio source. Amplifiers boost the audio signal and provide the headphones with sufficient power to ensure their maximum performance. The invention of transistors caused vacuum tube implementation to decline, leaving many audiophiles unsatisfied with the transistor’s sound signature. Vacuum tubes and transistors both amplify signals, however the distinct “tube sound” has vanished.

We have designed and created a product where the user selectively switches between solid-state transistor and tube amplification to compare the sound signatures of each amplification method. The ability to switch between the solid-state and …

Audio Dsp Amplifier, William Saba, Nicholas Barany

Electrical Engineering

The key concept of this project is to create a microcontroller system that serves as an interface between a DSP board and a total of 4 amplifier channels. The fully integrated system will provide a fully inclusive audio DSP amplifier for use in 2.1 or bi-amplified stereo speaker setups. The project will focus on developing an intuitive interface that is operable from the device or a computer that programs the DSP board for various speaker applications. The finished design will provide a custom computer sound amplifier in one package, eliminating the need for multiple components by interfacing two stereo amplifiers, …

Dual Channel Matrix Switch Audio Receiver, Austin Fox

Electrical Engineering

The Dual Channel Matrix Switch Audio Receiver controls 2 separate audio output channels. Each channel plays any of the system's 3 inputs. This controller enables a user to play two separate audio signals through two separate speaker channels. The system design allows audio input from 2 RCA sources or 1 RCA source and a phono source. The system outputs an audio signal for each output simultaneously at up to 36W on each channel for an 8Ω load. The device allows a user to control the audio input and the volume of each output channel. An Arduino Uno R3 microcontroller interfaced …

Multiplicative Feedback Audio Distortion Circuit, Colton Parsons

Electrical Engineering

This circuit aims to distort an audio signal input in a novel and aesthetically pleasing manner. When it comes to the timbre of a note, even harmonics generally sound better than odd harmonics. Most forms of audio signal distortion (usually for electric guitar) primarily add odd harmonics to a signal, as this is easily accomplished by clipping the waveform. This project instead utilizes a signal multiplier in a feedback loop, with one multiplier input coming from the circuit’s input, and the other from the multiplier’s own output. This process creates even harmonics. A delay line is placed in the loop, …

Digital Graphic Equalizer Implemented Using An Fpga, Anthony Giardina

Electrical Engineering

A graphic equalizer is a device that adjusts the tonal quality of an audio signal. When sound is converted from a digital format to analog sound waves, there are amplification and transducing steps in-between the two formats. Common devices to perform these tasks are speakers, amplifiers, DACs, etc. Many of these devices exhibit a non-uniform frequency response over the range of human hearing. Thus, it is possible that certain frequency ranges of the audio signal will be amplified and others will be attenuated. To counteract this, an audio equalizer can be used to boost and attenuate certain frequency ranges within …

Touch Screen Sound Controller, James Fenley, Jonathan Law

Electrical Engineering

The Touch Screen Sound Controller sets out to explore the use of a touch screen as a sound control interface for the disk jockey profession. In addition, the project aims to provide an alternate means of transferring audio data by way of TCP/IP communications as opposed to MIDI. By applying our method, a user may stream pulse-code modulated data from a server onto a client’s RAM via an Ethernet connection. A 32bit, 200MHz ARM9 microprocessor addresses data from the RAM and proceeds with executing DSP instructions from the user. The connection between the touch screen and the central microprocessor is …

Audio Thumbnail Generation Of Irish Traditional Music, Cillian Kelly, Mikel Gainza, David Dorran, Eugene Coyle

Conference papers

An approach is presented which generates an audio thumbnail of Irish traditional music. An audio thumbnail is consered to be the most representative segment of the music. For popular music, the chorus is considered to be an ideal audio thumbnail, however in Irish Traditional Music there is no chorus. An Irish Traditional tune consists of tow or mor short structural segments called parts. Parts are repeated to extend the tuen, and the tune itself is also repeated once or more in its entirety. To further extend a performance, tunes are concatenated to form a set of tuens. As a result, …

Psuedo-Randomly Controlled Analog Synthesizer, Jared Huntington

Electrical Engineering

The goal of this project was to design and build a portable box recreating classic sounds heard in science fiction films. These include sounds ranging from droning hums to bloops and bleeps. Currently no other device is made specifically for generating these sounds. The user controls and manipulates the sounds produced using a combination of switches and knobs to shape the sound generation. The sounds are generated using analog electronics. The project was successful in meeting the desired goal by designing and building a Randomizer, MIDI controller, VCO, LFO, VCA, Ring Modulator, and Fuzz Section. The resulting device is useful …