Dr. Piacsek's Lab

Quick introduction and background

My research involves sound and vibration: from musical instruments to sonic booms, from skull vibrations to wind turbine noise. The lab facility includes the anechoic chamber and the vibration lab with a scanning laser vibrometer (SLV), along with a variety of precision microphones and other sensors. Much of the data acquisition uses Labview. There is also a computational component to the lab: two high-performance Mac Pros and a PC run COMSOL, Matlab, Mathematica, and SoundPlan. In addition to learning about wave propagation and resonance behavior, students in the Acoustics lab acquire useful experimental and computational skills.

Project Descriptions

Quick List

1. Violin playing-in experiment: Does "pre-vibrating" a new violin make it sound better?

2. Using skull resonance to noninvasively monitor intracranial pressure (ICP)

3. Improving the acoustics of a commercial showroom/coffee shop in Portland

4. Develop a computer model to investigate wave propagation in tensegrity structures

5. Design and perform a test of the new anechoic chamber microphone positioning system

6. Investigate low frequency noise from commercial wind turbines

7. Other musical acoustics projects

a. Measure the formation of shock waves in wind instruments

b. Investigate the effect of the material that a flute is made of

Project 1

Investigation of how the tonal properties of a violin are affected by long-term playing

Background: Most performers of stringed musical instruments (such as violin, cello, and guitar) believe that a brand new instrument will improve its tone after it has been played for some time. This has led to a common practice among luthiers to "pre-vibrate" their instruments before they are sold. However, this phenomenon has not been thoroughly investigated and is not well understood.

Goal: Conduct careful experiments to establish and quantify a relationship between the vibrational exposure of a violin and its tonal properties.

Other information: We currently have three new violins on loan from Hammond-Ashley (a shop based in Issaquah). One is a control that will not be vibrated or played; the other two will be exposed to different levels of vibration intensity. Measurements include the vibrational response using the Laser Scanning Vibrometer and the radiated sound within the anechoic chamber.

Project type: experiment

Desired skills: basic knowledge of wave behavior (PHYS363 required)

Skills acquired: acoustic measurement and data acquisition; data analysis and signal processing

Instrumentation: microphone, accelerometer, laser scanning vibrometer, anechoic chamber

Software: Labview and Matlab

Project 2

Determine the feasibility of using skull resonances to monitor intracranial pressure

Background: Intracranial pressure (ICP) is the pressure of everything inside the skull, including brain matter and the surrounding cerebrospinal fluid (CSF). The body regulates this pressure within a fairly narrow range; sudden changes, such as when you stand up after napping on the sofa, can lead to dizziness. Trauma to the head or illness can lead to unhealthy or lethal increases of ICP. Currently, the only way to reliably measure ICP is invasive: a small hole must be drilled through the skull and a probe inserted. A noninvasive method for monitoring changes in ICP is highly desirable.

Goal: Precisely measure changes in the resonance response of human skulls due to changing internal pressure, with the objective of designing a portable apparatus for reliably monitoring ICP changes. Use of such an apparatus will be needed on long-term space flights.

Other information: Previous student research at CWU has demonstrated consistent frequency shifts in a spherical aluminum shell due to changes of pressure inside the shell. Preliminary measurements of cadaver skulls resonance frequencies have been made. The next step is to conduct rigorous trials of cadaver skull resonances while controlling the ICP.

Project type: experiment

Desired skills: basic knowledge of waves (PHYS363) and vibrations (PHYS341 preferred)

Skills acquired: vibration measurement and data acquisition; data analysis and signal processing

Instrumentation: accelerometer, laser scanning vibrometer

Software: Labview and Matlab

Project 3

Improve the acoustics in a commercial showroom in Portland

Background: The Bamboo Revolution showroom in Portland shares a large industrial space (formerly a car repair shop) with a coffee shop (of course). The coffee shop half of the room generates noise, mainly from conversation and background music. The objective is to reduce the noise level on the showroom side without building a full wall or partition. It is also desirable to use bamboo as part of any acoustic treatment.

Goal: Use a commercial software package to model sound propagation within the room and determine the optimal design and placement of hanging panels to reduce the sound transmission by satisfactory levels.

Other information: Previous student researchers at CWU have developed a basic computer model of the room and have tested the efficacy of placing a few panels with basic shapes. The next step is to improve the efficiency of the computation so that more complicated arrangements can be tested.

Project type: computer model

Desired skills: basic knowledge of waves (PHYS363); programming skills (PHYS361)

Skills acquired: understanding of sound in rooms; enhanced computational skills (assessing model output, optimization methods)

Software: SoundPlan

Project 4

Model waves in tensegrity structures

Background: Tensegrity structures were developed in the 1950's by Buckminster Fuller and Kenneth Snelson. They consist of two types of structural elements: struts support compressive forces and tendons support tension forces. They are interlaced so that the forces balance. Contrary to most structural designs, the struts are not in contact with other. Snelson made large-scale sculptures using tensegrity, but there are some practical architectural applications. Because they are lightweight for their size, they can be launched into space relatively inexpensively (in compact form), where they can be reassembled.

Goal: Create a model of a tensegrity structure in COMSOL and use it to investigate how waves propagate along the struts and tendons. Look for a frequency boundary below which the tensegrity structure acts like a continuous solid medium (with properties somewhat different from regular elastic solids), and above which the individual struts and tendons affect the wave like a lattice.

Other information:

Project type: computer model

Desired skills: basic knowledge of waves (PHYS363); programming skills (PHYS361)

Skills acquired: improved understanding of wave behavior; enhanced computational skills

Software: COMSOL

More to come...

Project 5

Test the behavior of the anechoic chamber with microphone positioning system

Project 6

Investigate low frequency sound propagation from commercial wind turbines