ECE 403

• Biomedical Imaging, Bioengineering, and Acoustics

Review of acoustics and signal processing, and development of a model of human hearing, followed by a number of real-world applications. Applications may include digital audio coding, audio recognition, design and analysis of auditoriums, audio localization/spatialization, and the design of loudspeakers, enclosures, and microphones.

To obtain an understanding of acoustics and signal processing fundamentals as they apply to the audio field. To facilitate an ability to read articles at the level of the Journal of the Audio Engineering Society. To contribute to a background useful for a position in the audio industry.

• Acoustics review and signal processing review
• Acoustic transducers
• Noise, intensity, and time-varying signals
• Auditory psychophysics
• Digital audio coding
• Room/auditorium acoustics
• Sound localization/spatialization
• Speech and audio recognition
• URL to home page: https://auditorymodels.org/index.php?n=Courses.ECE403-AudioEngineering-S19

To obtain an understanding of acoustics and signal processing fundamentals as they apply to the audio field. To facilitate an ability to read articles at the level of the Journal of the Acoustical Soc of Am. and Journal of the Audio Engineering Society (Publications not open to non-members). To contribute to a background useful for a position in the audio industry.

Topics:

• Acoustics review and signal processing review
• Acoustic transducers (Loudspeaker fundamentals)
• Noise, intensity, and time-varying signals
• Auditory psychophysics
• Digital audio coding
• Room/auditorium acoustics
• Sound localization/spatialization
• Speech and audio recognition

Matlab exercises

Final group lab report

Characterize how a loudspeaker works: Lab manual: https://jontalle.web.engr.illinois.edu/uploads/403///LabManual.pdf

Hardware provided by Instructure that can measure the complex transfer function from 0.05-20 kHz. This is used to characterize the loudspeaker characteristics [input impedance, frequency resp (magnitude and phase)]

Octave or Matlab on laptop computers

• Passive circuit steady-state and transient analysis (ECE 210)
• Acoustic plane and spherical wave phenomena (ECE 473)
• Fourier and Z transform (ECE 310)
• IIR and FIR filter design (ECE 310)

Course notes and various published articles.

http://www.sciencedirect.com.proxy2.library.illinois.edu/science/book/9780123914217

Beranek, Leo Acoustics, Wiley 1950 (reprinted by the Acoustical Society of Am, AIP)

Engineering Science (Electro-Acoustics): 3 credits or 100%

Goals

• Audio Engineering is the practical integration of Electroacoustics, Psychoacoustics, and Signal Processing for the purpose of creating really cool stuff.
• Electroacoustics: The study of speakers, mics, and other things that make electrical signals acoustic and vice versa.
• Psychoacoustics: The study of pitch,loudness, timbre, masking, and other perceptual qualities of a sound.
• Signal Processing: The study of filters and spectral representations used for signal description, interpre­tation, or compression.
• After learning about the core theoretical areas, we will study one or more of the following application areas.
• Room Acoustics: The art of measuring, modeling, and simulating the presence, early echoes and rever­beration of a room.
• 3D Audio Spatialization: The art of reproducing sounds at specified apparent locations around the listener.
• Pre-requisites are digital signal processing(ECE310) and acoustics(ECE373). The level is advanced undergraduate or introductory graduate.

By the time of the midterm exam, students should be able to do the following:

1. Under stand how a loud speaker works: Electrical input impedance, transfer functions (pressure out/current in), Acoustic output impedance, Rayliegh Reciprocity.

2. Write the acoustic wave equation and its solutions, in both time domain and phasor representation, for a plane wave and for a spherically symmetric wave (1,6)

3. Compute the frequency response and impulse response of a duct, or of a rectangular room (1,6)

4. Given a matrix frequency response representing a two-port system, calculate the one-port frequency response that results from constraints on any two of the inputs (1,6)

5. Compute the magnitude and phase response of a speaker/microphone pair given tonepip measurements at different frequencies (1,6)

6. Analyze an equivalent circuit to calculate the magnitude and phase response of a moving armature loudspeaker, electrostatic loudspeaker, electrodynamic microphone, or condenser microphone (1,6)

7. Create a desired microphone directivity pattern by scaling and adding omnidirectional and figure-eight patterns (1,6)

8. Calculate the loudness of a sound made up of spectrally distinct tones and noise bands (1,6)

9. Determine whether or not one simple sound (tone or noiseband) will perceptually mask another (1,6)

By the time of the final exam, students should be able to do all of the above, plus the following:

1. When we study room acoustics: use the image source method to calculate the impulse response and reverberation time of a rectangular room. Students should also be able to calculate reverberation time using Sabine’s formula,given the geometry of the room, a description of the wall coverings, and a table of material absorptivities.

2. learn how a loudspeaker works

3. Analyize loudspeaker action

4. Measure loudspeaker impedance

5. Formulate a model of a loudspeaker based on ABCD matrix analysis

5. Demonstrate knowledge of Thevenin characteristics of a loudspeaker

6. Explain reciprocity in loud speaker analysis

ECE 403 includes a small final project, intended to be roughly equivalent to a normal computer assignment. The final project should demonstrate that a student can

1. Understand an article from the professional literature well enough to implement the algorithm it describes (1,3,6)

2. Compose a written report that demonstrates understanding of the theoretical motivation of the algo­rithm and the meaning of results (1,5,6,7)