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Sound Power Level: PowerPoint Presentation
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Sound Power Level:

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  1. Amazing dB’s Sound Pressure Level: Sound Power Level: The main thing to remember is that 100 dB sound pressure level and 100 dB sound power level are completely different! To avoid confusion, use the reference values: 100 dB (re 20 Pa) sound pressure level 100 dB (re 1x10-12 W) sound power level 1

  2. But they are related… S in m2 (no reflections) (Spherical source) r (Hemi-spherical source) S = cross-sectional area (duct) r 2

  3. An Example A source has a sound power level of 90 dB (re 10-12 W). What is the sound pressure level at a distance of 10 m in (a) a free field, (b) in a hemispherical free field, and (c) in a duct of cross-sectional area 1 m2? a. b. c. 3

  4. Numerical Acoustics Field Quantities p, u = sound pressure and particle velocity in the field. How do we determine these? un= velocity of surface in normal direction – must be known 4

  5. Two Vacuums Shopvac Bosch 5

  6. Bosch Vacuum Exhaust flows through foam 6

  7. Shopvac Vacuum 7

  8. Sound Power Exhaust Deflected Upward 8

  9. Time and Frequency Domains 9

  10. Sound Power Comparison – Bosch, All Sides 10

  11. Sound Power Comparison – Narrow Band 11

  12. Sound Power Comparison at Low Frequency Low Frequency Tone 12

  13. Sound Power Comparison – 1/3 Octave 13

  14. Sound Quality Bosch (original) Bosch (w/o foam) Shopvac Bosch (w/o 1st peak) 14

  15. Sound Quality: Jury Test Note: Rate each vacuum on a scale from 1 to 10 where 1 is “very quiet” and 10 is “very loud.” 15

  16. Foam Inside Bosch Vacuum 16

  17. Sound Absorption Coefficient 17

  18. Sound Absorption Coefficient of Foam 18

  19. Sound Intensity (Shopvac) 19

  20. Sound Intensity (Bosch) 20

  21. Sound Intensity (Bosch) 21

  22. Summary • Absorption of foam in BOSCH significantly reduces sound power • Sound exhaust is better directed on BOSCH • Recommend altering design to reduce/shift first peak 22