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Frequency Analysis - Noise Control - Lab Manual, Study notes of Noise Control

National Institute of Industrial EngineeringNoise Control

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, Sound Power, Noise Barriers, Outdoor Sound Propagation, Helmholtz Resonator and Vibration Control. Key points of this lab manual are: Frequency Analysis, Power Hand Tool Analysis, Fft Analysis, Loudness of a Machine, Physical Characteristics of the Source, Microphone Location, Noise

Typology: Study notes

2012/2013

Uploaded on 10/02/2013

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ME458 Lab 2 8/17/2000 page 1
ME458 Noise Control
Laboratory Exercise #2
Frequency Analysis
Objectives:
1. Measure the frequency response of physical systems using FFT analysis.
2. Relate the measured frequency response to physical characteristics of the source.
3. Calculate the loudness of a machine
Part 1: Power Hand Tool Analysis
Procedure: Measure the frequency response of two machines. Measure the octave band
levels using a sound level meter. Measure the sound pressure as a function of frequency
using the FFT analyzer. Choose an appropriate frequency scale (you may choose to use
more than one plot) that shows interesting data and provides enough resolution to
separate frequency peaks. Relate peaks in the frequency response to physical
characteristics of the source (rotation speed, # of fan blades, # of gear teeth, etc.).
Test Conditions:
Test location – 22 Hammond
Noise sources - Power hand drill, ILG source, Centrifugal blower
Microphone location - 0.5 meters from source
Instrumentation - (list model and serial number information here)
Instrument Manufacturer Model Serial #
Sound level meter
FFT analyzer
Microphone
Noise Source 1:
Octave Band Sound levels (dBLinear)
32 Hz 64 125 250 500 1000 2000 4000 8000
dB
pf3

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ME458 Noise Control

Laboratory Exercise

Frequency Analysis

Objectives:

  1. Measure the frequency response of physical systems using FFT analysis.
  2. Relate the measured frequency response to physical characteristics of the source.
  3. Calculate the loudness of a machine

Part 1: Power Hand Tool Analysis

Procedure: Measure the frequency response of two machines. Measure the octave band levels using a sound level meter. Measure the sound pressure as a function of frequency using the FFT analyzer. Choose an appropriate frequency scale (you may choose to use more than one plot) that shows interesting data and provides enough resolution to separate frequency peaks. Relate peaks in the frequency response to physical characteristics of the source (rotation speed, # of fan blades, # of gear teeth, etc.).

Test Conditions: Test location – 22 Hammond Noise sources - Power hand drill, ILG source, Centrifugal blower Microphone location - 0.5 meters from source Instrumentation - (list model and serial number information here)

Instrument Manufacturer Model Serial # Sound level meter FFT analyzer Microphone

Noise Source 1:

Octave Band Sound levels (dBLinear) 32 Hz 64 125 250 500 1000 2000 4000 8000 dB

Relation of frequency peaks to physical causes Frequency - Hz Cause of peak

Attach frequency response plots

Noise Source 2:

Octave Band Sound levels (dBLinear) 32 Hz 64 125 250 500 1000 2000 4000 8000 dB

Relation of frequency peaks to physical causes Frequency - Hz Cause of peak

Attach frequency response plots

Homework 2. (hand in separately) Using the octave band levels data you just obtained, calculate the overall loudness of the two machines. What octave band contributes most to the loudness? If you could redesign the machines to make it less loud, what would you change first?