Abstract No:
1123
Abstract Type:
Professional Poster
Authors:
E Massawe1
Institutions:
1Southeastern Louisiana University, Hammond, LA
Presenter:
Ephraim Massawe, Sc.D.
Southeastern Louisiana University
Description:
Sound is a mechanical wave characterized by frequency, wavelength, and amplitude, with noise defined as unwanted sound. Frequency, measured in Hertz (Hz), determines pitch, while decibels (dB or dBA) quantify sound intensity on a logarithmic scale-higher decibel levels correspond to louder sounds.
This study investigates how sound intensity varies indoors with distance and frequency, a critical concern for fields such as occupational health, safety, environmental science, acoustics, architecture, civil engineering, and noise control in venues like movie theaters and lecture halls. Understanding these dynamics is essential for managing noise pollution, which can affect human health, comfort, and productivity in both work and non-work environments.
The primary goal of this research is to analyze how noise levels change across different indoor workspaces, providing insights to inform improved environmental design and effective noise mitigation strategies.
Materials Used:
Monotone Noise Frequency Generator (capable of producing 2000 Hz, 4000 Hz, and 8000 Hz tones)
Electronic sound level meter (SLM) (for measuring decibels), Casella 63X, Digital SLM (https://casellasolutions.com), Fig 1.
Calibration device for noise SLM at 1000 Hz and 114 dBA
Measuring tape or ruler (for distance measurement), https://www.amazon.com/Measure-Mileseey-Distance-switching-Pythagorean/dp/B0863RK1KX?th=1
Controlled indoor environment within the Computer Science and Industrial Technology
Situation / Problem:
Noise is a significant health hazard in both occupational and non-occupational settings, causing a broad range of auditory and non-auditory effects. Occupational noise exposure, particularly above 85 dBA, can lead to irreversible noise-induced hearing loss (NIHL) and is common in industries such as construction, manufacturing, mining, transportation, and entertainment. In addition to hearing loss, occupational noise contributes to cardiovascular problems, stress, decreased productivity, communication difficulties, and a higher risk of accidents.
Non-occupational noise pollution from sources like traffic, personal audio devices, and social events also poses serious health risks. It disrupts sleep, leading to fatigue and increased cardiovascular disease risk, and adversely affects mental health by elevating anxiety, depression, and psychological distress. Moreover, noise exposure can impair cognitive functions, especially in children, impacting attention, memory, and learning.
Noise influences health through direct auditory and brain system pathways, as well as indirect cognitive and emotional responses. This study evaluates mitigation strategies aimed at reducing noise-related harm in indoor microenvironments, focusing on variations with distance and exposure duration.
Methods:
Materials Used:
Monotone Noise Frequency Generator (capable of producing 2000 Hz, 4000 Hz, and 8000 Hz tones)
Electronic sound level meter (SLM) (for measuring decibels), Casella 63X, Digital SLM (https://casellasolutions.com), Fig 1.
Calibration device for noise SLM at 1000 Hz and 114 dBA
Measuring tape or ruler (for distance measurement), https://www.amazon.com/Measure-Mileseey-Distance-switching-Pythagorean/dp/B0863RK1KX?th=1
Controlled indoor environment within the Computer Science and Industrial Technology (CS&IT) Building
Procedure:
Generated monotone noise at 2000 Hz, 4000 Hz, and 8000 Hz frequencies
Measured the noise levels at different distances from the source (0, cm, 200 cm, 400 cm, 800 cm, 1600 cm, and 3200 c).
Repeated these measurements for all three frequencies
Recorded the data and analyze the results.
model equation (unable to upload) ----
a is the noise-wave amplitude decay, with higher values of a suggesting stronger decay from the sources.
c is the approximate noise level at large distances from the source
Results / Conclusions:
Results / Conclusions
Frequency-dependent attenuation: Higher frequencies (8000 Hz) attenuate more rapidly than lower frequencies (2000 Hz) due to shorter wavelengths and increased environmental absorption.
Distance effect: Sound (noise) intensity decreases with distance following the inverse square law, with an approximate 6 dB reduction each time the distance doubles.
Frequency comparison:
2000 Hz (cycles/per second) maintained the highest intensity over distance.
8000 Hz (cycles/per second) showed the fastest decay rate.
4000 Hz (cycles/per second) had the highest variability (±10.4 dBA), suggesting reflections/interference.
Modeling: Exponential decay fits confirmed increasing decay rates with frequency.
Statistical analysis: Significant differences exist in attenuation rates between frequencies.
Conclusions:
Sound attenuation is strongly frequency-dependent, with higher frequencies experiencing faster decay.
Noise control strategies should account for frequency-specific propagation characteristics, especially in industrial settings.
Environmental factors (e.g., reflections) significantly impact mid-frequency sound measurements, requiring controlled testing conditions.
Recommendations: Employ calibrated microphones for future studies, increase measurement points and trials, and conduct tests in acoustically controlled environments to reduce variability and improve accuracy.
Implications:
These results support the development of targeted noise mitigation strategies, enhance hearing conservation programs, and improve noise mapping accuracy by integrating frequency and distance-dependent attenuation models.
Core Competencies:
Noise and Hearing Loss Prevention
Secondary Core Competencies:
Noise and Hearing Loss Prevention
Work Environments, Occupations, and Industrial Processes
Choose at least one (1), and up to five, (5) keywords from the following list. These selections will optimize your presentation's search results for attendees.
Hearing conservation and noise reduction
Risk assessment and management
Based on the selected primary competency area of your proposal, select one group below that would be best suited to serve as a subject matter expert for peer review:
(Select one)
Noise Committee
Based on the information that will be presented during your proposed session, please indicate the targeted audience practice level: (select one)
Technician: Technician is a job title given to persons who are trained to assist professionals and practitioners with task-specific assignments. Technicians may collect air samples, operate direct-reading instruments, and provide other services based on specific training received and instructions received from professionals and practitioners.
Was this session organized by an AIHA Technical Committee, Special Interest Group, Working Group, Advisory Group or other AIHA project Team?
No
Are worker exposure data and/or results of worker exposure data analysis presented?
No
How will this help advance the science of IH/OH?
This research advances Industrial Hygiene and Occupational Health by clarifying how sound frequency and distance interact to affect noise attenuation in workplace environments. By quantifying the more rapid attenuation of higher frequencies compared to lower frequencies, the findings support more precise noise exposure assessments and targeted noise control strategies.
Accurate characterization of frequency-specific attenuation and variability in noise reduction enhances survey and mapping techniques. This enables industrial hygienists to better predict exposure levels across various locations within a facility-particularly at mid-frequencies where environmental factors introduce greater variability-leading to improved measurement protocols and data reliability. These insights facilitate optimized placement of engineering controls, personal protective equipment, and hearing conservation efforts, ultimately improving worker safety and reducing the risk of occupational hearing loss.
By integrating frequency- and distance-dependent attenuation models, this work advances predictive noise assessments and regulatory compliance, thereby strengthening protections for worker auditory health.
What level would you consider your presentation content geared towards?
Intermediate: Specific topics within a subject. The participant would have two (2) to ten (10) years experience in industrial hygiene or OEHS and a good understanding of the subject area, but not of the specific topic presented. Prerequisites required: another course, skill, or working knowledge of the general subject.
Have you presented this information before?
No
I have read and agree to these guidelines.
Yes