MMAN9325 LAB 2

.docx

School

University of New South Wales *

*We aren’t endorsed by this school

Course

9325

Subject

Mechanical Engineering

Date

Oct 30, 2023

Type

docx

Pages

Uploaded by fakenandshaken

MECH9325 Laboratory 2 – Measurement of Sound Power Anthony Ngo-Le, z5312271 Submission date: 25/07/2023 By submitting this work, I acknowledge that the intellectual content of this report is my own, except where the contributions of others are explicitly described and/or properly cited. I am familiar with my responsibilities under the UNSW Student Code and understand how UNSW defines plagiarism and academic integrity.

Table of Contents 1. Introduction ....................................................................................................................................... 1 2. Procedure .......................................................................................................................................... 1 2.1 Direct method .............................................................................................................................. 2 2.2 Comparison method .................................................................................................................... 2 3. Results ............................................................................................................................................... 3 3.1 Direct method results .................................................................................................................. 3 3.2 Comparison method results ......................................................................................................... 3 3.3 Comparison of direct method and comparison method .............................................................. 4 4. Discussion .......................................................................................................................................... 4 5. Summary ........................................................................................................................................... 4 References ............................................................................................................................................. 5 Table of Figures Figure 1: Microphone positions on the hemispherical measurement surface for a broadband noise source [1] ............................................................................................................................................... 1 Figure 2: Graph showing the relationship between the average SPL of the drill vs. the octave band centre frequency .................................................................................................................................... 4 Table of Table Table 1: The averaged measured sound pressure location across 10 locations .................................... 3 Table 2: Data calculated using the direct method to find sound power level of the electric drill .......... 3 Table 3: Data calculated using the comparison method to find sound power level of the electric drill.3 i

1. Introduction The objective of this laboratory is to evaluate the sound power levels of a noise source, that source being an electric drill. The laboratory will be completed using a common engineering method which is used for essentially free fields near a reflecting plane. The testing can be conducted in a semi-reverberant field such as a large, spacious room or near a hard ground surface if testing outdoors. Further elaboration of the engineering method applied can be found in Australian Standard AS 5335:2019, which details how to correctly compute an environmental correction for reverberation effects. The method itself is comprised of two different approaches: the direct method and the comparison method. 2. Procedure The octave sound pressure level (SPL) of an electric drill was measured at 10 different locations within a hemispherical surface with a radius of 1 m. Figure 1: Microphone positions on the hemispherical measurement surface for a broadband noise source [ CITATION Kes \l 3081 ] To determine the average measured sound pressure level at each octave band centre frequency (L p(S) ), the following equation was applied, ´ L p ( S ) = 10log 10 ( 1 N ∑ i = 1 N 10 L pi 10 ) Where i = 1: N ( N = 10 ) . Subsequently, the sound power level of the noise source was calculated through either the direct method or the comparison method. The result for each octave band centre frequency was then unweighted, as the original SPL measured was A- weighted previously.

MMAN9325 LAB 2

Browse Popular Homework Q&A