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  • Spectra Tech Ltd: Sound Masking System Tuning, Open Plan Office Speech Privacy, Setup, Adjustment, Onsite Field Testing Services, Design Services, ASTM WK8777, Richard Lemker, Nationwide, Ohio, Indiana, Kentucky, Cincinnati, Dayton, Columbus, Springfield, Bowling Green, Knoxville, Portsmouth, Louisville, Lexington, Indianapolis, Frankfort, Lima, Bloomington, Huntington, WVA, OH, IN, KY

    Spectra Tech employes sophisticated equipment and software to measure, document, and adjust the output of sound masking systems in open plan office spaces and other facilities where speech privacy is an important consideration. We can also provide assistance in designing sound masking systems to optimize privacy.

    • The Privacy Index (PI) was developed by Dr. Robert Chanaud to form a universal standard by which the privacy of speech communication within a given acoustical environment could be quantified. The test can also be used to measure and document the intrusion of undesirable noise and music.
    • To test the Privacy Index value between two locations, one must measure the "source" location sound level (normal speech, raised voice, music, etc), the sound attenuation provided by elements of intervening construction (walls, cubicles, etc), the background noise level at the "receiving" location, and the amount of signal enhancement (this usually only applies to locations where security is mandatory, e.g. a US government SCIF) available to the listener at the receiving location.
    • To determine the "source" sound level, a direct measurement can be taken at the location, or test data for typical sources previously documented can be used.
    • To test the transmission of sound through a particular construction, a broadband spectrum of noise is generated at all frequencies between 63 Hz and 16,000 Hz and amplified to provide a level at the receiving side that is sufficiently higher than the room's normal ambient noise level.
    • The average unweighted (fast response) sound levels for each octave frequency band between 125 Hz and 8,000 Hz (8KHz) is recorded at ten random locations on the "source side" of the construction for a period of 10 seconds or more.
    • The average unweighted (fast response) sound levels for each octave frequency band between 125 Hz and 8,000 Hz (8KHz) is recorded at ten random locations on the "receiving" location for a period of 10 seconds or more.
    • A reverberation time test is also conducted in the "receiving room" and if the room reverberation is not found to be within the nornal criteria, adjustments to the rating must be made accordingly.
    • The final Privacy Index (PI) value is then computed and expressed as a percentage. A PI value of 100% indicates 100% privacy (0% intelligibility).
    • When Privacy Index values are found to be less than targeted, the deficienciy data is used as the basis for tuning a sound masking system to generate the required sound spectrum.
    • Our Test System can also compute other speech intelligibility / speech privacy values for the given situation, including Articulation Index (AI), Speech Intelligibility of Sentences First Heard (SISF), and Speech Intelligibility of Sentences Known (SISK). Please see the technical notes below for an explanation of these variables.
    • Areas / rooms throughout your entire facility can be tested for compliance with the targeted performance crieteria. If defieicenies are identified, we can make adjustments and / or assist in developing solutions.
    • Plot / Print Test Results: We can provide documentation of test results by plotting / printing the test values on paper, and / or provide the reslts in PDF format.


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