Setting Targets for Acoustic Design

Size: px

Start display at page:

Download "Setting Targets for Acoustic Design"

Katrina Allen
8 years ago
Views:

1 Setting Targets for Acoustic Design Kaj Dam Madsen DELTA DANSIS Meeting at DELTA 5. October 2005

2 Presentation Outline Short discussion of acoustic design criteria Presentation of simple method for - choosing the appropriate design criteria, - use as guidance during the design process and - most important to make the target understandable for everyone involved

design criteria, - use as guidance during the design process and

3 Acoustic Design Criteria Noise Levels - Sound Power levels, L WA db(a) - Sound Pressure levels, L pa db(a) Criteria for audible tones Criteria for impulses Frequency band limitations Sound Quality parameter targets -,, Roughness Annoyance criteria How do you make it possible to involve all relevant persons to set up a common and understandable acoustic design criteria and use is to control the design process?

parameter targets -,, Roughness Annoyance criteria How do you make it possible to involve all relevant

4 Case Study: Noise Reduction of Adflo Fresh Air Helmets To meet new market and keep customers happy: Reduce A-weighted noise level Reduce noise annoyance Keep fresh air performance Make minimum changes to design

Reduce A-weighted noise level Reduce noise annoyance

5 Step 1: Overview and Definition of Solution Space Preliminary investigations Noise Levels, db(a) Frequency Analysis Design Review Findings: Tonal noise from fan Broadband flow noise High Frequency tonal noise from fan regulator

Analysis Design Review Findings: Tonal noise from fan

6 Possible Measures to improve the Acoustic Design Tonal noise reduction: Impeller design - Number of blades - Edge design - Blade spacing Tongue design Active damping Broadband flow noise Straightening of fan outlet Passive broadband damper

design - Blade spacing Tongue design Active damping

7 Step 2: Choosing the Target for Acoustic Design Reference situation known Noise sources known Solution space defined What is our target? To be decided amongst people from Sales, Development, Production, Quality Assurance and Management

8 Sound Quality Profile Characteristic Parameters (sone) Metric for the perceived intensity of sound. - (acum) The sensation of sharpness is produced by highfrequency components in acoustic signals. strength (vacil) strength is the sensation associated with amplitude modulation at low frequencies (approx. 4 Hz). Roughness (asper) The sensation of roughness results from amplitude or frequency modulation of a sound at frequencies between 15 Hz and 300 Hz. Audible tones (db/m) Audible tones in noise is perceived as humming, houling or whistling depending on the frequency of the tones. 71 db(a) Prominence of impulses An impulse is defined as the sudden onset of a sound. Stop

strength (vacil) strength is the sensation associated with amplitude modulation at low frequencies (approx. 4 Hz).

9 Speedglass-helmet in Original Design Library of Different Filters and Operating Conditions Scaled profile: S-P-L Scaled profile: S-ABE-L Scaled profile: S-AA-L A B C Roughness 64 db(a) 68 db(a) 72 db(a) Scaled profile: S-P-H Scaled profile: S-ABE-H Scaled profile: S-AA-H D E F db(a) 71 db(a) 73 db(a) Stop

10 Helmet simulated passive damper* Original Passively damped * 0 db below 300 Hz, -10 db above 800 Hz Tone component from fan Stop

11 Helmet simulation of tone damped 10 db* Original Damped * Change of fan or/and active damping Tone component from fan Stop

12 Library of Different Design Changes (simulated) Scaled profile: S-ABE-H Reference sound Scaled profile: S-ABE-H-10 Tone damped 10 db Scaled profile: S-ABE-H-15 Tone damped 15 db db(a) 67 db(a) 66 db(a) Scaled profile: S-ABE-H-P Passive damping, 10 db - Scaled profile: S-ABE-H-10P Passive and tone 10 db - Scaled profile: S-ABE-H-15P Passive and tone 15 db - Stop 64 db(a) 62 db(a) CHOOSE YOUR TARGET SOUND! 62 db(a)

13 Step 3: Design 5 different impellers - Increase of blade number - Change of blade exit angle - Random blade position Tongue modification Passive damper design - Reflection - Absorption Prototypes as SLA models

blade position Tongue modification Passive damper

14 Results Best impeller version - Tonal noise reduced by up to 13 db - A-weighted level reduced 8-10 db Passive damper 7-10 db reduction of A-weighted level RefMin A1Minx A2Min A3Min A4Min

reduction of A-weighted level 80 70 60 50 40 RefMin A1Minx

15 Validation of Results Reference Target Prototype Tone prom. Roughness 71 db(a) 62 db(a) 63 db(a) Stop

16 Conclusions - Test Case Solutions found to give - appropriate impact on existing models, - easily implemented solutions to new products, - tonal damping up to 13 db, - A-weighted damping up to 15 db for some conditions, - les annoyance SQ profile was used as a tool for common understanding and choice of appropriate target sound profile The library concept was very popular an easy to handle

17 Acoustic Design and Product Development Cycle Product Specification Design Verification & Validation Production/ Marketing/ After Sales Review concept Listening tests Setting targets - 71 db(a) Design rules Experience Empirics Simulation - BEM, FEM -CAA,. Prototype testing and troubleshooting Accredited tests: - Sound Power - Sound Pressure Listening tests Sound Quality Profile Sound Quality Profile Product review Troubleshooting - 71 db(a)

Experience Empirics Simulation - BEM, FEM -CAA,.

18 Conclusions Awareness of noise characteristics throughout the product development cycle is important The Sound Quality Profile can be used - as a common and understandable target description for the product development cycle, - to keep everyone on the (same) track - to communicate targets across company function borders and different levels of acoustical knowledge

description for the product development cycle, - to keep everyone on the (same) track - to

19 Yderligere interesse for Produktlyd? Forslag til dannelsen af en erfagruppe om produktlyd i SPM - regi er på vej Kontakt KDM@DELTA.DK

Noise from large wind turbines (with focus on low frequencies)

Noise from large wind turbines (with focus on low frequencies) Christian Sejer Pedersen M.Sc. EE., Ph. D. Associate professor Acoustics, Department of Electronic Systems, Aalborg University Fredrik Bajers