Air Conditioning and Automatic Heating Systems Gilbert & Barker Mfg.

Branches 8t.

Air System Equipment Fans and Blowers Hartzell Propeller Fan Co.

Air System Equipment Motors APPARATUS DEPARTMENT GENERAL ELECTRIC SCHENECTADY.

Air System Equipment Fans and Blowers Blower Wheels The Lau Blower Company 2007 Home Avenue, Dept.

Heating Systems BoUers, o,s Hook & Ackerman, Inc. 63-56 Shakespeare St. 18 East 41st St.

290 ASHRAB Guide And Data Book 4A iV^wryomat'c DIVISION OF LOGETRONICS* INC.

Industrial Noise in age produce an increasing loss which starts at the high frequency end of the spectrum After sixty, few persons can hear beyond 10,000 or 12,000 Hz However, the maxi mum sensitivity range of the ear is between 1000 and 4000 Hz Before discussing hearing loss, let us first decide what constitutes normal hearing "Normal hearing" is defined as the average hearing of a group of persons considered essentially representative of the population Normal hearing has been designated only for the following frequencies 250, 500, 1000, 2000, 4000, and 8000 Hz m the audible spectrum For any one of the chosen fre quencies hearing is measured in units called "decibels of hearing level " Some areas of the audible spectrum are more important than--others, for example -- the speech range as represented in a conven tional pure tone audiogram, 500, 1000 and 2000 Hz The value at these frequencies will indicate quite accurately how well a person can hear and understand speech Another area in the audible spectrum im portant to the person interested m noise extends through 3000, 4000, and 6000 Hz Although these frequencies have no signifi cant relation to the understanding of speech, they are a sensitive indicator of the onset and progress of noise-induced hearing loss Hear ing tests are designed to test hearing by way of the external ear, called air conduction tests, and the skull, or bone conduction tests Remember that the reference points for normal hearing are average values obtained by testing a large group of individuals An average figure implies that manv of the indi viduals tested are either better or worse than average Because of this, normal hearing should not be thought of as a specific level, but rather as an area extending 15 dB (deci bels) on either side of the average value Audiometry The field of audiometry (hearing measure ment) now embraces pure tone audiometry, speech audiometry, screening audiometry, group audiometry, and recently, automatic audiometry The electronic audiometer is the instrument commonly used to measure hearing It is necessary when using the general term "audi ometer" to specify which type of instrument is meant a pure tone audiometer, speech audiometer, screening audiometer, automatic audiometer, group audiometer, and others which are beyond the scope of this Manual The choice of measurement technique and the type of audiometer is dictated by the pur pose for which the test is being made Audiometry may be divided into two broad subfields, based on the sound stimulus used (a) pure tone audiometry and (b) speech audiometry' Pure tone audiometry i used primarily to determine air conduction and bone conduction thresholds of hearing These thresholds are necessary for diagnostic evaluations of hearing loss Pure tone air conduction threshold tests and pure tone air conduction screening tests are also used extensively in industrial and school hearing conservation programs Speech audiometry is used principally to obtain speech reception thresholds and speech discrimination scores for diagnostic purposes and to evaluate the performance of hearing aids Pure tone audiometry.

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INTERROGATORY NO. 123: If your answer to Interrogatory No. 122 is "Yes," then with respect to each such inspection, test or survey: (a) Identify the governmental entity conducting the same; ______(b).....State the datesCsXon^whidiJihasame-was QQndu&tect;--- (c) Describe the nature of the inspection, test or survey including, but not limited to, the results or conclusions thereof; and (d) Identify any and all documents referring to, relating to or reflecting the same.

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206-02-2 Drum Brake REMOVAL AND INSTALLATION (Continued) 206-02-2 Removal and Installation WARNING: Asbestos fiber dust can be present on brake and clutch assemblies and Is hazardous to health if inhaled.