Acoustical Laboratories and Research Programs
The facilities which are available to the students and faculty of the Acoustics Program for their research can be found in various laboratories located throughout the campus, each administered separately by the departments to which they are connected. For some idea of the extent of the facilities available and research projects in progress, see the descriptions below:
APPLIED RESEARCH LABORATORY
The Applied Research Laboratory (ARL) is the largest of eleven interdisciplinary research units at Penn State. Sponsored almost exclusively by the U.S. Navy, ARL supports over fifty applied and basic research projects related to acoustics. Acoustic research at ARL is mainly related to underwater applications and includes such topics as: radiated noise; gear noise generation; vibration control using constrained layer damping and compound isolation mounts; materials for acoustic absorption and transmission; flow and acoustic induced vibrations; hydrodynamic flow noise; acoustic scattering and diffraction; structural acoustics; underwater sound propagation, particularly reverberation and bottom loss effects; adaptive signal and array processing; high-resolution image processing; acoustic signal analysis; sonar guidance and control; and electro-acoustic transducers.
Researchers at the Applied Research Laboratory have an excellent selection of equipment and facilities with which to conduct their research including two underwater anechoic tanks, three high pressure tanks, an underwater reverberation chamber, a noise analysis room, four water tunnels, a glycerine tunnel, a wind tunnel, a tow tank, a clean room for transducer fabrication, a general acoustics laboratory, specialized vibration and materials laboratories, as well as machine shops and electronic construction facilities.
THE ARL ANECHOIC CHAMBER
A large anechoic chamber is located in the Garfield Thomas Water Tunnel Building. The chamber is designed to allow air to flow through noiselessly at 18,000 cubic feet per minute. The acoustical cut-off frequency of 70 Hz makes it one of the lowest frequency chambers available for testing air moving devices. The chamber can be configured as a conventional anechoic chamber, or a hemi-anechoic chamber or as a special diagnostic tool for measuring radiated sound from non-steady flows.
The uniqueness of the chamber is due to its combined features; the large volume, the quality of the air flow, and the flexibility of configuration.
The chamber has been used in several thesis research projects including studies of automotive HVAC systems, automotive alternators, gear noise, flow transitions, separated flows, active fan noise control, and vacuum cleaner noise control.
NOISE CONTROL LABORATORY
College of Engineering
Research conducted at the Noise Control Laboratory encompasses a great many industrial and product applications including such topics as: fan noise; jet noise; duct acoustics; valve noise and its reduction; automotive engine noise; and noise reduction devices like mufflers and resonators. In addition, the laboratory is involved in investigating the influence on outdoor noise propagation of terrain, forests and other vegetation, particularly their contribution to the control of highway and airport noise.
Facilities available to support these and other projects include: an environmentally controlled anechoic room (14 ft. x 17 ft. x 9 ft.); a 5000 cubic foot reverberant room; an instrumentation and data analysis facility, including a high speed 16 channel Masscomp data acquisition and processing system; a freon loop; and a mercury ripple tank and a laser facility.
ACOUSTO-OPTIC IMAGING LABORATORY
Engineering Science and Mechanics Department
The acousto-optic imaging laboratory is a facility for visualization and quantification of acoustic fields. The facility can visualize the acoustic field generated by either acoustic emission, radiation, or scattering. The facility can also be used to measure the acoustic impedance of materials, pinpoint defects and faults inside bulk materials and structural components, identify sources of noise emission and diffraction, and identify paths of structural wave propagation.
The laboratory includes a Schlieren System, an electronic imaging system, supporting computer facilities, and associated data recording.
ACOUSTIC INTENSITY LABORATORY
Graduate Program in Acoustics
The Acoustic Intensity Laboratory conducts research on advanced techniques for measuring the complex acoustic intensity vector, particle velocity and sound pressure existing in actual acoustic fields. Examples of the types of studies for which sound intensity measurements have been made include: the sound field radiation and the nearfield studies of discrete source configuration; the sound power radiation and modal behavior of thin steel plates; the sound field mapping for sound interference in ducts; the mapping of diffracted sound field behind noise barriers; the detailed studies of the sound radiator coupling on loudspeaker enclosures; and the noise radiation from an impact excited printing wheel.
The laboratory facilities consists of a computer-controlled three-dimensional mechanical scanner; a four-microphone probe to measure two components of intensity simultaneously; and various digital recording and processing equipment for data analysis and source identification and analysis systems.
ACOUSTIC LABORATORY
Physics Department
The research being conducted in the Acoustics Laboratory of the Physics Department includes the investigation of the following topics: sound radiation from plates of different shapes including those that are used in musical instruments; effects of ribbing on the plate vibrations and the radiation of sound; nearfield acoustic holography techniques for analyzing sound sources; cryogenic studies of shear viscosity of fluids, in the frequency range of 100 kHz to 10 MHZ; and diffraction studies on three-dimensional bodies, made in an anechoic chamber, in which Keller's and Freeman's echo theories are compared with experimental results.
The facilities that are available in the laboratory for these and other research projects include: a laboratory for studies of plate vibrations; a laboratory for diffration studies, a unit for absorption measurements in liquids; facilities for acoustical holography (computer assisted); and a laboratory for cryogenic studies.
SHOCK AND VIBRATION LABORATORY
Engineering Science and Mechanics Department
The Shock and Vibration Laboratory is established to conduct basic and applied research on the dynamic analysis of simple and complex structures. Examples of the types of research projects the laboratory is involved in include: the modal analysis of a rocket-assisted projectile consisting of three interconnected shells; shock testing and analysis of optimum nonlinear shock mounts, shock testing of nonlinear beams under combined tension and bending, including a theoretical analysis; evaluating data from tests of pyrotechnic separation joints; and a theoretical prediction of submarine hull vibration based on a 800 degree-of-freedom representation which includes mounts, foundation, decks, and hull framing.
Laboratory facilities include a drop-table shock machine; both large and small electromagnetic shakers; various signal and noise generators; and essential electronic equipment for acquiring processing, recording, displaying and analyzing measured data.
DYNAMIC MATERIALS LABORATORY
Applied Research Laboratory and Polymer Science Department
The Dynamic Materials Laboratory conducts research on the dynamic and acoustic properties of polymers and composites. The laboratory is involved in: determining the dynamic modulus and loss factor of elastomeric materials including novel combinations of polymers and piezoelectric materials for improved damping; accessing the dynamic response of metal matrix and polymer matrix composites; tailoring polymer blends and composites with specific acoustic or dynamic properties; designing materials that are acoustically transparent as well as materials with desired anechoic or decoupling characteristics.
The laboratory has at its disposal: a laser vibrometer system and related apparatus for determining the dynamic properties of materials over a wide range of frequencies, temperatures and pressures; various instruments for characterizing the morpholopy, rheology and relevant physical properties of polymers; and an air-filled standing wave tube and two water-filled pulse tubes for determining the acoustic impedance and reflection, absorption transmission coefficients of acoustic materials; as well as data acquisition and analysis instrumentation.
DYNAMIC RESPONSE LABORATORY
Applied Research Laboratory
The Dynamic Response Laboratory is a facility for vibration testing and the experimental investigation of the dynamic response of structures. Instrumentation available includes a laser vibrometer system consisting of a vibrometer, FFT analyzer, translation system, and apparatus that is supported on an air-suspended optical bench; a modal analysis system which has a spectrum analyzer and associated hardware, equipment and software; and a digital speckle-pattern interferometer.
Other equipment at ARL that may be used in conjunction with the foregoing are a hydraulic pump noise testing apparatus and a flow visualization condenser. Additional unique equipment, specifically designed and constructed at ARL, includes a simple mass-spring vibrator device and test fixturing for vibrating mechanical systems such as the clamped circular plate, simply-supported rectangular plate, and a two-stage, 1800-pound seismic mass and large vibration generator. A file is available that contains more than 200 FORTRAN computer programs for use in comparing experimental measurements with certain predicted vibration responses of damped mechanical systems.
Current projects include research on the vibration properties of composite materials, noise control of bearings and gears, noise generation in two phase flow, and vibration and sound radiation from structures.
HEARING RESEARCH LABORATORY
Communication Disorders Program
The Hearing Research Laboratory contributes to the basic knowledge and technological application of acoustics, audiology, electronics, physics, occupational health, and shock and vibration. It operates on an interdisciplinary basis through the Communication Disorders Program and emphasizes studies in hearing protection, instrumentation, effects of sound and vibration on man, standards and regulations, communication and communications systems, new techniques for therapy and education of the deaf, noise surveys, and general environmental noise problems.
Facilities include mechanically and electrically isolated quiet rooms, an anechoic chamber, and instrumentation and test areas. Modern equipment includes general-purpose and precision instrumentation, as well as portable instruments and accessories for measuring, processing, recording and analyzing acoustical and audiological data.
MEDICAL ULTRASONICS LABORATORY
Bioengineering Program
The Medical Ultrasonic Laboratory conducts basic research on the ultrasonic transmission and scattering characteristics of body tissue and organs. Laboratory facilities include sector and linear array real-time scanners; doppler flowmeters to measure transcutaneous blood-flow; various microcomputers, digitizers and display peripherals; assorted ultrasonic transducers and wideband hydrophones; and water tanks with positioning devices.
ULTRASONIC DIAGNOSTICS LABORATORY
Engineering Science and Mechanics Department
The Ultrasonic Diagnostics Laboratory is involved in research in fracture and fatigue, tribology, and materials characterization. This research is now concentrated on sequential failure in polymeric and metal matrix composites. Research also involves the ultrasonic detection of sub-surface flaws induced by machining and grinding.
The laboratory facilities consists of equipment suitable for ultrasonic non-destructive evaluation including: various signal and pulse generators; both dual delay and master synchronizer generators; power amplifiers, impedance matching networks and high resolution frequency sources; a gated peak detector; assorted ultrasonic transducers and hydrophones; and related spectrum analyzers and recorders.
Graduate Program in Acoustics, The Pennsylvania State University
