OUR PEOPLE

Daniel Mennitt

Ph.D., P.E., INCE Bd. Cert.

Mechanical Engineering

Managing Engineer

Denver

Office: +1-303-802-3428

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Academic Credentials

Ph.D., Mechanical Engineering, Virginia Polytechnic Institute and State Univ, 2008
B.S., Mechanical Engineering, Virginia Polytechnic Institute and State Univ, 2004

Licenses & Certifications

Professional Engineer, Colorado, #PE.0058367
Professional Engineer, Wisconsin, #48642-6
Board Certified

Academic Appointments

Research Scientist III, Department of Electrical and Computer Engineering, Colorado State University, 2018-2019
Research Scientist II, Department of Electrical and Computer Engineering, Colorado State University, 2015-2018
Research Scientist I, Department of Electrical and Computer Engineering, Colorado State University, 2010-2015
Graduate Research Assistant, Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, 2004-2008

Professional Honors

The Robert Bradford Newman Medal for Merit in Architectural Acoustics, 2005
Best Paper By A Young Presenter, 153rd Meeting of the Acoustical Society of America, 2007.

Professional Affiliations

Acoustical Society of America
Institute of Noise Control Engineering
American Society for Testing and Materials: ASTM Committee E33 on Building and Environmental Acoustics

Dr. Mennitt specializes in acoustics and is skilled in the characterization, design, and modeling of acoustical environments and devices. His primary areas of expertise include noise and vibration control, environmental noise, signal processing, and auditory perception. Dr. Mennitt is board certified by the Institute of Noise Control Engineering.

Dr. Mennitt has applied his expertise to noise and vibration control of machines, buildings, infrastructure, medical devices, and consumer products. He has developed and implemented solutions to effectively reduce noise transmission to sensitive areas, isolate vibration, and support the development of quieter products. Dr. Mennitt conducts testing to characterize acoustical quantities such as sound power, directivity, transmissibility, and frequency response. He also draws on analytical methods and numerical models to evaluate mechanisms of sound generation, dominant sources, and transmission paths.

Dr. Mennitt's work is rooted in the human response to sound and vibration. As a certified Occupational Hearing Conservationist, he has evaluated occupational noise exposure, hearing conservation programs, hearing protection devices, and the efficacy of mitigative measures to protect hearing in the workplace and other settings. He has conducted assessments of whole body and hand transmitted vibration. Other work related to human perception has involved the audibility of alarms, annoyance of noise, speech intelligibility, and evaluation of product sound quality.

Dr. Mennitt has worked extensively with federal agencies and other organizations to assess environmental noise and the effects of noise exposure on humans and ecological systems. Prior to joining Exponent, he worked at Colorado State University in partnership with the National Park Service's Natural Sounds and Night Skies Division to manage acoustical environments. His research involved the spatiotemporal patterns of environmental sound on landscape scales, acoustical transducers, bioacoustics, flow noise, and predictive modeling. Dr. Mennitt has designed acoustical devices and methods for data acquisition, calibration, and monitoring sound in extremely quiet environments. While at Colorado State University, Dr. Mennitt also taught a course on acoustics, noise, and signal processing.

Dr. Mennitt's experience in computational acoustics includes deterministic time and frequency domain simulations of acoustic propagation (FEA, BEM, FDTD) as well as applications that exploit statistical learning. He led a multidisciplinary team to pioneer technology that uses geospatial data to generate comprehensive maps of environmental sound levels and noise exposure on continental scales. He has worked with academia, government, and industry to translate these estimates to implications for land management, ecological, epidemiological, military, and commercial applications. Dr. Mennitt's signal processing experience extends to active sonar applications, adaptive noise and echo control, and development of algorithms for detection, estimation and classification.

Dr. Mennitt's background is in mechanical engineering. He performed his doctoral work at Virginia Tech's Vibration and Acoustics Laboratory, developing terrestrial sonar systems for localization and tracking of acoustic sources in free-field and cluttered environments. During this research, he developed robust statistical methods for classification of acoustical signals and fusion of information from distributed sensor networks. He has also created tools for signal detection, beamforming, adaptive filtering, speech processing, and array signal processing. While at the Vibration and Acoustics Laboratory, he conducted testing with anechoic and reverberation rooms, intensity probes, impedance tubes, modal impact hammers, accelerometers, and shakers. Other graduate work included applications in spatial audio, active noise control for signal enhancement, architectural acoustics, music production, and audio engineering. His training and expertise in audio engineering helps Dr. Mennitt conduct educated and critical observations to address acoustical issues.

Noise Control Engineering
- Conducted acoustical measurements and developed models to characterize the sound emission of noise sources associated with machines, consumer electronics, consumer products, medical devices, and other equipment. Identified dominant noise sources, mechanisms of sound radiation, and transmission paths using models in conjunction with experimental sound and vibration data.
- Prescribed and optimized noise controls such as acoustical enclosures and damping treatments to provide sufficient noise reduction within design constraints.
- Evaluated occupational noise exposure, hearing conservation programs, and the efficacy of mitigative measures to protect employee hearing.
- Measured the attenuation of active noise cancelling headphones and passive hearing protection devices in the laboratory to determine their capability to reduce noise exposure.
- Applied analytical models of sound radiation to develop test methods for ultrasonic acoustic sources and evaluated the effects of human exposure to ultrasound.
- Characterized the acoustic performance of a wearable electronic device and conducted measurements to evaluate regulatory compliance with international standards.
- Characterized processes to estimate peak sound levels associated with impulsive noise from impacts.
- Determined the root cause of impact noise and vibration in a machine and specified mitigation to control noise.
Environmental Noise and Vibration
- Conducted environmental noise studies of industrial facilities, construction activities, utilities, as well as road, rail, and other transportation projects to assess the potential for community noise complaints and other environmental impacts; provided assistance through all aspects of project development including planning, mitigation, construction, and post-construction compliance testing.
- Designed, executed, and analyzed acoustic field surveys of ambient conditions outdoors in urban communities and remote areas. Typical applications have included noise source characterization, assessment of existing conditions, insertion loss of controls, and post-construction noise emissions for regulatory compliance.
- Modeled acoustic propagation from noise sources to estimate the potential impacts to local communities, determine compliance with regulations, and assess noise mitigation strategies.
- Prepared noise control plans for construction activities such as the installation of underground power transmission lines and drilling operations.
Building Vibration and Room Acoustics
- Evaluation of sound transmission in buildings including measurement of architectural acoustic parameters such as sound transmission class, impact insulation class, outdoor indoor transmission loss, absorption, and reverberation time.
- Designed experiments and conducted path analyses to determine the root cause of noise and vibration transmission in a residential apartment building; implemented mitigation to effectively isolate vibration and reduce noise transmission to sensitive areas in a building.
- Conducted field measurements of airborne and ground-borne noise and vibration arising from roadways and rail systems to evaluate human exposure and response in residential and other buildings.
- Developed numerical models and conducted field measurements to assess the sound transmission of building facades and highway noise abatement strategies.
- Evaluated the potential effects of floor transmitted vibration on sensitive equipment in laboratories and offshore platforms from transportation and machinery sources.
- Assessed HVAC noise controls in commercial buildings and vehicles to resolve deficiencies and mitigate occupant annoyance.
- Evaluated floor-ceiling assemblies to assess impact noise in buildings and prescribed renovation options to mitigate construction deficiencies and noise problems.
Auditory Perception
- Evaluated the audibility of alarms and other sound sources, such as vehicles and aircraft, under various environmental conditions.
- Assessed the effect of hearing protection devices on recognition of warning signals in background noise.
- Conducted measurements of acoustic events to evaluate their subjective perception using psychoacoustic metrics such as tonality, sharpness, and time-varying loudness.
- Devised screening criteria for acceptable sound quality of a quieter product based on acoustical metrics and spectral data.
- Instrumented and analyzed the interior sound field of vehicles to evaluate the driver's auditory experience and related NVH (noise, vibration and harshness) metrics.
- Design of experiments to assess speech intelligibility associated with a telecommunications device.
- Analyzed the characteristics of sources to assess human response to whole body vibration in vehicles.
Signal Processing
- Engineered sonar systems for military, industrial, and consumer applications.
- Designed and implemented array signal processing algorithms such as adaptive beamforming and generalized sidelobe cancellers.
- Evaluated the accuracy of a multirate signal processing system using a heterodyne receiver.
- Formulated signal processing algorithms and designed filters for detection, classification, and enhancement of audio signals such as speech.
- Identified noise mitigation strategies and engineered techniques to improve the accuracy and robustness of an active sonar system.
- Designed octave band and fractional-octave-band digital filter banks to efficiently calculate sound pressure levels from audio data; demonstrated performance in accordance with national standards.
- Instrumentation and testing of vehicles to evaluate component function and acoustic transmission. Conducted a vibroacoustic analysis of drivetrain components and identified the mechanism of noise generation in a vehicle using coherent output power techniques.
- Developed voice activity detectors and devised metrics to evaluate the efficacy of an acoustic echo canceller for telecommunications.
- Conducted forensic audio analyses and prepared demonstrative courtroom exhibits.
Flow Induced Noise and Vibration
- Measured meteorological, sound, and vibration data to determine the root cause of wind-induced flow noise and vibration affecting outdoor infrastructure; implemented mitigation to control noise emissions.
- Conducted and evaluated acoustical measurements to characterize the sound power of noise sources in HVAC equipment; identified feasible strategies to reduce the A-weighted noise level and increase speech intelligibility in classrooms.
- Determined the dominant noise transmission paths in a fan enclosure using analytical calculations and experimental sound and vibration data.
- Investigated a flow induced resonance in a steam pipeline and designed noise controls to reduce structural vibration.
- Designed acoustic absorbers to control flow noise in a medical device which could not use typical porous materials.
- Formulated lumped parameter models to estimate the resonant characteristics of a duct excited by flow.
Nondestructive Testing and Failure Analysis
- Conducted failure analysis of a piezoelectric transducer and enclosure.
- Provided design support for the development of a vibroacoustic sonar system operating underground.
- Engineered instrumentation and protocols to assess the effect of vibration on nondestructive evaluation of gas pipelines that account for vibroacoustic interaction of pipe shell and fluid dynamics. Analyzed measurement data to assess piping vibration sources and the risk of vibration induced fatigue failure in natural gas and water pipelines.
- Characterized the performance of piezoelectric transducers, including phased arrays for ultrasound imaging and acoustic source localization, using empirical data, analytical methods, and finite element models.
- Instrumented turbomachinery and analyzed condition monitoring data to identify component failure and determine maintenance requirements.
- Conducted experimental modal analysis of vibrating structures to determine root cause of failure in conjunction with finite element analyses.
- Conducted laser doppler vibrometer measurements to determine the effects of vibration on thermal performance of a consumer electronic device. Measured the dynamics of a lightweight structure in a consumer product using laser doppler vibrometry to solve problems related to fatigue and NVH (noise, vibration, and harshness).
- Evaluated medical ultrasound devices including hydrophone measurement of high intensity therapeutic shock waves to demonstrate compliance with regulatory guidance.
Selected Publications
Ferguson L.A., Taff B.D., Blanford J.I., Mennitt D.J., Mowen A.J., Levenhagen M., White C., Monz C.A., Francis C.D., Barber J.R., Newman P., "Understanding park visitors' soundscape perception using subjective and objective measurement," PeerJ 12 (2024):e16592.
M. Senzaki, J. R. Barber, J. N. Phillips, N. H. Carter, C. B. Cooper, M. A. Ditmer, K. M. Fristrup, C. McClure, D. J. Mennitt, L. P. Tyrrell, J. Vukomanovic, A. A. Wilson and C. D. Francis, "Sensory pollutants alter bird phenology and fitness across a continent," Nature 587 (2020):605-609.
R. T. Buxton, M.F. McKenna, D. J. Mennitt, E. Brown, K. Fristrup, K.R. Crooks, L. M. Angeloni, G. Wittemyer, "Anthropogenic noise in US national parks — sources and spatial extent," Frontiers in Ecology and the Environment 17 (2020): 559-564.
D. J. Mennitt, "An adaptive coupler for the calibration of the arbitrarily shaped microphones," Applied Acoustics 154 (2019):114-120.
K.E. Rudolph, A. Shev, D. Paksarian, K.R. Merikangas, D.J. Mennitt, P. James, and J. A. Casey, "Environmental noise and sleep and mental health outcomes in a nationally representative sample of urban US adolescents," Environmental Epidemiology, 3 (2019): e056.
D. J. Mennitt, K. Fristrup, and B. Notaros, "Characterization of gain and directivity of exponential horn receivers," The Journal of the Acoustical Society of America, 142 (2017):3257-3266.
R. T. Buxton, M. F. McKenna, D. J. Mennitt, K. M. Fristrup, K. Crooks, L. Angeloni, and G. Wittemyer, "Noise pollution is pervasive in US protected areas." Science 356, no. 6337 (2017):531-533.
D. J. Mennitt and K. Fristrup, "Influential factors and spatiotemporal patterns of environmental sound levels in the contiguous United States," Noise Control Engineering Journal, 64 (2016):342-353.
D. J. Mennitt, K. Fristrup, and K. Sherrill, "A geospatial model of ambient sound pressure levels in the contiguous United States," The Journal of the Acoustical Society of America 135 (2014):2746-2764.
D. J. Mennitt, K.M. Fristrup, "Obtaining calibrated sound pressure levels from consumer digital audio recorders," Applied Acoustics 73 (2012):1138-1145.
K. M. Fristrup, and D. J. Mennitt. "Bioacoustical monitoring in terrestrial environments." Acoustics Today 8(2012):16-24.
D. J. Mennitt, and M. Johnson, "Multiple-array passive acoustic source localization in urban environments," The Journal of the Acoustical Society of America, 127.5 (2010): 2932-2942.
M. Ermann, M. R. F. Kidner, and D. J. Mennitt, "Mapping the sound field of a 400 seat theater," Building Acoustics 13.3 (2006):199-210.
Selected presentations, proceedings, and seminars
K. Spak and D. J. Mennitt, "Vibration specifications and standards as part of EPC contracts," VIATC 45th Vibration Institute Annual Training Conference (2023).
J. A. Casey, A. Shev, D. Paksarian, K. R. Merikangas, D. J. Mennitt, and K. E. Rudolph, "Association between exposure to noise and sleep and mental health outcomes in a nationally-representative sample of U.S. adolescents," 2018 Annual Conference of the International Society for Environmental Epidemiology (2018).
M. F. McKenna, D. J. Mennitt, M. Thompson, J. Stanley, S. Van Parijs, K. M. Fristrup, and L. Hatch, "Including acoustical features in marine ecological prediction," NOAA-Navy Workshop: Soundscape Metrics to Support Marine Protected Area Management, Woods Hole Oceanographic Institution, MA (2018).
D.J. Mennitt, D. Joyce, and K. Fristrup, "Benefits and challenges of using consumer audio equipment for unattended acoustical monitoring," The Journal of the Acoustical Society of America, 144, 1828 (2018).
D. J. Mennitt, M. F. McKenna, and K. M. Fristrup, "Continental perspectives of noise exposure and its effects," INTER-NOISE and NOISE-CON Congress and Conference Proceedings, 255 (2017):1168-1172.
D. J. Mennitt, "Classification of wind induced pseudo noise using low resolution features," National Park Service, Natural Resource Stewardship and Science, Fort Collins, CO (2017).
D. J. Mennitt and K. Fristrup, "Gain and directivity of exponential horn receivers," The Journal of the Acoustical Society of America 140, 3140 (2016).
D.J. Mennitt and K. Fristrup, "Anomaly detection and other practical considerations for estimating acoustical metrics from time series data," The Journal of the Acoustical Society of America, 140, 3424 (2016).
D. J. Mennitt and K. M. Fristrup, "A geospatial approach to mapping environmental sound levels across the United States," American Society for Photogrammetry and Remote Sensing, Geobytes (2016).
P. James, R. Banay, D. J. Mennitt, K. Fristrup, J. Africa, J. Hart, F. Laden, "Noise and Cardiovascular Disease in a Nationwide Cohort Study," 28th Annual Conference of the International Society of Environmental Epidemiology, Rome, Italy (2016).
D. J. Mennitt, L. Hatch, K. M. Fristrup, M. Thompson, D. Cholewiak, M. F. McKenna, P. Auster and S. Van Parijs, "A geospatial approach to exploring the soundscape of Stellwagen Bank National Marine Sanctuary," Oceanoise 2015, Vilanova i la Geltrú, Spain (2015).
D. J. Mennitt, E. Brown, and K.M. Fristrup, "Assessing the condition of acoustical resources across the National Park Service Units," 2015 George Wright Society Conference on Parks, Protected Areas, and Cultural Sites, Oakland, CA (2015).
M. F. McKenna, K. M. Fristrup, and D. J. Mennitt, "Predicting historic and current sound levels from point measurements: a geospatial model," Science for Parks, Parks for Science: The Next Century, Berkeley, CA (2015).
D. Risch, P. Auster, D. Cholewiak, K. Fristrup, L. Hatch, M. McKenna, D. Mennitt, M. Thompson, and S. Van Parijs, "Monitoring bio-acoustic activity & geospatial models of ambient sound: Applications in a marine sanctuary," Ecology and acoustics: emergent properties from community to landscape, Paris, France (2014).
D. J. Mennitt, "Spatial variation of natural ambient sound pressure levels in Rocky Mountain National Park." The Journal of the Acoustical Society of America 129, 2617 (2011).
M. Ermann, J. Carneal, D. Mennitt, C. Jackson, B. Karmarkar, M. Helveston, and P. Clay, "Sound transmission loss of nontraditional building materials and redundancies," The Journal of the Acoustical Society of America 122(5) (2007).
D. J. Mennitt, M. Johnson, and J. Carneal, "Coarse classification of acoustic signals using temporal and spectral characteristics," Journal of the Acoustical Society of America 121(5):3046 (2007).
J. Carneal, M. Johnson, D. J. Mennitt, and P. Gillett, "Localization and tracking noise sources with autonomous vehicles: from node processing to central command fusion and tracking," Acoustical Society of America's North Carolina Chapter, Raleigh, NC (2006).
D. J. Mennitt, "Numerical accuracy of virtual acoustic prototyping: determination of the minimum size of the evaluation sphere to achieve accurate local simulation," Acoustical Society of America's North Carolina Chapter, Raleigh, NC (2006).
D. J. Mennitt, P. Gillett, J. Carneal and M. Johnson, "Tracking Noise Sources Using Multiple Mobile Microphone Arrays," Thirteenth International Congress on Sound and Vibration, Vienna, Austria (2006):1-8.

Daniel Mennitt

Project Experience

Publications

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Patents