Acoustic Materials - Noise Control - Lab Manual, Study notes for Noise Control. National Institute of Industrial Engineering

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Some of topics included in this course are: Fundamentals of Acoustics, Levels and Decibels, Divergence and Directivity, Hearing, Human Response to Noise, Frequency Analysis, Sound Sources and Fields, Room Acoustics, Soun...
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ME458 Noise Control

ME458 Lab 4 8/17/2000 page 1

ME458 Noise Control Laboratory Exercise #4

Acoustic Materials and NC Rating of Rooms

Objectives:

1) Measure the sound absorption coefficients of porous materials using a standing wave tube (Impedance Tube)

2) Determine the NC rating of several spaces and compare to recommended values Part 1: Acoustic Materials Using the B&K impedance tube, determine the normal incidence absorption coefficient, statistical absorption coefficient and the impedance for 2 different materials. Compare your results to published values of absorption coefficients. Material: Freq Hz Lpmax Lpmin D1 D2 αn Z/ρc αstat Published

value of α 125 250 500 1000 2000

Material: Freq Hz Lpmax Lpmin D1 D2 αn Z/ρc αstat Published

value of α 125 250 500 1000 2000

List of Formulas Used: αn= Z/ρc= αstat=

ME458 Lab 4 8/17/2000 page 2

Part 2: Room Noise Criteria Objectives: Measure the background level (in full octave bands) in at least three different classrooms, offices, or concert halls around campus. From this data, calculate the NC rating of each space and compare to the recommended values for these spaces.

Center Freq (Hz) A B C 32 64 125 250 500 1000 2000 4000 8000

overall NC rating

Recommended NC rating (ASHRAE)

Description of rooms: A B C Reporting Requirements: Submit a brief, concise lab report. Include: Instrumentation details, data tables, graphs of NC contours, comments

ME458 Lab 4 8/17/2000 page 3