Sound Masking Systems Sound Masking Systems by Ashton Taylor, Hoover & Keith Inc. A technical guide to achieving effective speech privacy in open-plan offices and other environments 1601 Jack McKay Blvd. • Ennis, Texas 75119 U.S.A. Telephone: 800.876.3333 • Fax: 800.765.3435 – 1 – AtlasIED.com Specifications are subject to change without notice. Sound Masking Systems Introduction Reduction of Reflected Sound Energy ......................................... 13 What is Sound Masking? ............................................................... 4 Ceiling ................................................................................... 13 The Economic Benefits of Sound Masking .................................... 4 Absorption Ratings ............................................................... 13 Purpose of this Paper ..................................................................... 4 Noise Reduction Coefficient ................................................. 13 Part 1 - A Discussion of Sound Masking Articulation Class .................................................................. 13 Applications for Sound Masking Systems ...................................... 5 Lighting Fixtures ................................................................... 14 Open-Plan Offices Definition of Terms ................................... 5 Masking Loudspeakers and the Ceiling........................................ 14 Medical Examination Rooms .................................................. 5 Special Ceiling Tiles .............................................................. 14 Confidential Offices ................................................................ 5 Sound Leaks ......................................................................... 14 Court Rooms .......................................................................... 5 Other Causes of Unwanted Reflections ....................................... 15 Buildings Near Major Roads, Railroads, & Airports ................ 5 Boots .................................................................................... 15 Personal Masking Units .......................................................... 5 Ambient Noise .............................................................................. 17 Security Systems ................................................................... 6 Part 3 - The Basic Electronic Sound Masking System When Sound Masking Should Not Be Used .................................. 6 Concept - Don’t Tell the Employees? ............................................ 18 Unrealistic Client Expectations ............................................... 6 Self-Contained Masking Units ...................................................... 18 Rooms Requiring Very Low Ambient Noise ........................... 6 Single-Channel vs Multi-Channel Masking ........................... 18 Space Used by Sight-Impaired People ................................... 6 Basic Electronics .................................................................. 18 Space Used by Hearing-Impaired People ............................... 6 Sound Masking and Background Music or Paging ....................... 19 Benefits of Masking to the End User ............................................. 7 Basic System Electronics ............................................................. 19 Cost-Effective Speech Privacy ................................................ 7 Masking Sound Generator ................................................... 19 Increased Productivity ............................................................ 7 Equalizer ............................................................................... 19 Flexibility ................................................................................. 7 Amplifier ............................................................................... 19 Part 2 - The Sound Masking Acoustical Environment Part 4 - Multi-Channel Masking, Background Music and Paging Three Steps to Successful Sound Masking ................................... 8 Two (and More) Channel Masking ................................................ 21 1 - Attenuate the Direct Sound .............................................. 8 Zone Level Controls ............................................................. 21 2 - Reduce Sound Reflections ................................................ 8 Amplified Monitor Panel ....................................................... 21 3 - Raise the Ambient Sound Level Using Sound Masking.... 8 Background Music / Paging .......................................................... 22 Discussion .............................................................................. 8 Paging Sound Level .............................................................. 22 A Basic Sound Masking Example ................................................... 8 Paging Equalizers .................................................................. 22 Evaluating the Acoustical Environment .......................................... 9 Part 5 - Masking Loudspeakers and Self-Contained Masking Units Attenuation of Direct Sound ......................................................... 10 Masking Loudspeakers ................................................................. 23 Orientation of Talker ............................................................. 10 Upwards Loudspeaker Orientation ....................................... 23 Screens ................................................................................ 10 Downwards Loudspeaker Orientation .................................. 24 Sound Transmission Class .....................................................11 Horizontal (Sideways) Loudspeaker Orientation ................... 24 Diffraction ..............................................................................11 Valuable Masking Loudspeaker Features ............................. 24 Layout ................................................................................... 12 Self-Contained Masking Units ...................................................... 25 1601 Jack McKay Blvd. • Ennis, Texas 75119 U.S.A. Telephone: 800.876.3333 • Fax: 800.765.3435 AtlasIED.com – 2 – Specifications are subject to change without notice. Sound Masking Systems Part 6 - Commissioning the Masking System Appendix A - Definitions ............................................................ 37 Level ............................................................................................. 26 Appendix B - Worksheet ............................................................ 39 Connecting Spaces ............................................................... 26 General Instructions ..................................................................... 39 Setting the Level During System Adjustment ...................... 26 Entering the Data ................................................................. 39 Gradually Adjust to Final Level ............................................. 26 Calculating the Speech Level at the Listener ....................... 39 Masking Spectrum ....................................................................... 27 Calculating the Articulation Index ......................................... 39 Ideal Masking Sound Spectrum ........................................... 27 Detailed Worksheet Instructions .................................................. 40 Masking Spectrum 1 ............................................................ 28 Section A Instructions .......................................................... 40 Masking Spectrum 2 ............................................................ 28 Section B Instructions .......................................................... 40 Masking Spectrum 3 ............................................................ 28 Section C Instructions .......................................................... 41 A Comparison of All Three Masking Spectra ........................ 29 Section D Instructions .......................................................... 42 Equalizing the System .................................................................. 29 Section E Instructions .......................................................... 43 The Equalization Process ...................................................... 29 Section F Instructions ........................................................... 44 Using an Octave-Band Equalizer for ..................................... 30 Section G Instructions .......................................................... 44 Coverage ...................................................................................... 30 Section H Instructions .......................................................... 45 Test Equipment ............................................................................ 30 Section I Instructions ............................................................ 45 Part 7 - Predicting Privacy in the Masking Environment Section J and Section K Instructions ................................... 46 Articulation Index and Privacy Category Definitions ..................... 31 Section L Instructions ........................................................... 46 Subjective Speech Intelligibility Articulation Index ............... 31 Sound Masking, Octave-Band, Articulation - Index Worksheets Marginal Privacy ................................................................... 31 Worksheet Example 1 - Open-Plan Environment ......................... 47