Pattern approval for measuring instruments

Courtesy: Pattern approval for measuring instruments

Sound level meters

• IEC61672 Ed. 2.0 (2013)
• IEC60651 Ed 1.2 (2001) plus Amendment 1 (1993-02) and Amendment 2 (2000–10)
• IEC60804 (2000–10)
• ANSI S1.4-2014 (a U.S. nationally adopted international standard from IEC 61672:2013)

Octave filters

• IEC61260 Ed. 1.0 (2014) Electroacoustics – Octave-band and fractional-octave-band filters
• ANSI S1.11-2004 (R2009)

Personal noise dosimeters

• IEC61252 Ed. 1.1 (2002–03)
• ANSI S1.25-1991(R2007)

Measurement microphones

• IEC 61094 : 2000

Room acoustics

• ISO 3382-1:2009 Measurement of Room Acoustic Parameters Part 1: Performance Rooms
• ISO 3382-2:2008 Measurement of Room Acoustic Parameters Part 2: Reverberation Time in Ordinary Rooms
• ASTM E2235 (2004) Standard Test Method for Determination of Decay Rates for Use in Sound Insulation Test Methods.
• Equipment safety
• IEC61010-1 Ed. 2.0 (2001–02)
• International standards
• The following International standards define sound level meters, PSEM and associated devices. Most countries’ national standards follow these very closely, the exception being the USA. In many cases the equivalent European standard, agreed by the EU, is designated for example EN 61672 and the UK national standard then becomes BS. EN 61672.
• IEC 61672 : 2013 “Electroacoustics – sound level meters”
• IEC 61252 : 1993 “Electroacoustics – specifications for personal sound exposure meters”
• IEC 60942 : 2003 “Electroacoustics – sound calibrators”
• IEC 62585 : 2012 “Electroacoustics – Methods to determine corrections to obtain the free-field response of a sound level meter”
• These International Standards were prepared by IEC technical committee 29:Electroacoustics, in cooperation with the International Organization of Legal Metrology (OIML).
• Until 2003 there were separate standards for exponential and linear integrating sound level meters, but since then IEC 61672 has described both types. The classic exponential meter was originally described in IEC 123 for ‘industrial’ meters followed by IEC 179 for ‘precision’ meters. Both of these were replaced by IEC 651, later renamed IEC 60651, while the linear integrating meters were initially described by IEC 804, later renamed IEC 60804. Both IEC 60651 and 60804 included four accuracy classes, called “types”. In IEC 61672 these were reduced to just two accuracy classes 1 and 2. New in the standard IEC 61672 is a minimum 60 dB linear span requirement and Z-frequency-weighting, with a general tightening of limit tolerances, as well as the inclusion of maximum allowable measurement uncertainties for each described periodic test. The periodic testing part of the standard (IEC61672.3) also requires that manufacturers provide the testing laboratory with correction factors to allow laboratory electrical and acoustic testing to better mimic Free field (acoustics) responses. Each correction used should be provided with uncertainties, that need to be accounted for in the testing laboratory final Measurement uncertainty budget. This makes it unlikely that a sound level meter designed to the older 60651 and 60804 standards will meet the requirements of IEC 61672 : 2013. These ‘withdrawn’ standards should no longer be used, especially for any official purchasing requirements, as they have significantly poorer accuracy requirements than IEC 61672.
• Military standards
• Combatants in every branch of the United States’ military are at risk for auditory impairments from steady state or impulse noises. While applying double hearing protection helps prevent auditory damage, it may compromise effectiveness by isolating the user from his or her environment. With hearing protection on, a soldier is less likely to be aware of his or her movements, alerting the enemy to their presence. Hearing protection devices (HPD) could also require higher volume levels for communication, negating their purpose.
• MIL-STD 1474D The first military standard (MIL-STD) on sound was published in 1984 and underwent revision in 1997 to become MIL-STD-1474D. This standard establishes acoustical noise limits and prescribes testing requirements and measurement techniques for determining conformance to the noise limits specified herein. This standard applies to the acquisition and product improvement of all designed or purchased (non-developmental items) systems, subsystems, equipment, and facilities that emit acoustic noise. This standard is intended to address noise levels emitted during the full range of typical operational conditions.
• MIL-STD 1474E In 2015, MIL-STD 1474D evolved to become MIL-STD-1474E which, as of 2018, remains to be the guidelines for United States’ military defense weaponry development and usage. In this standard, the Department of Defense established guidelines for steady state noise, impulse noise, aural non-detectability, aircraft and aerial systems, and shipboard noise. Unless marked with warning signage, steady state and impulse noises are not to exceed 85 decibels A-weighted (dBA) and, if wearing protection, 140 decibels (dBP) respectively. It establishes acoustical noise limits and prescribes testing requirements and measurement techniques for determining conformance to the noise limits specified herein. This standard applies to the acquisition and product improvement of all designed or purchased (non-developmental items) systems, subsystems, equipment, and facilities that emit acoustic noise. This standard is intended to address noise levels emitted during the full range of typical operational conditions. This standard includes two methods for assessing the impulse noise and risk to hearing.
  • The Auditory Hazard Assessment Algorithm for Humans (AHAAH), a one-dimensional electro-acoustic analog of the auditory system, produced MIL-STD 1474E’s numerical guidelines. Over time the predictability of this algorithm has been claimed to have increased to 95% accuracy. US Army Research Laboratory researchers state that almost every error resulted in overcalculation of risk. By comparison, the MIL-STD-147D was deemed correct in 38% of cases with the same data. Originally developed from a cat animal model and later informed by human data, the AHAAH sums the basilar membrane displacements of 23 locations.The AHAAH model calculates the estimated displacement of the basilar membrane and summates the accumulation of the flexure of the basilar membrane. The user inputs their noise exposure, protection level, and whether they were forewarned of the noise, to receive their hazard vulnerability in auditory risk units (ARU). This value can be converted to compound threshold shifts and the allowed number of exposure (ANE). Compound threshold shifts is a value that integrates both temporary and permanent shifts in auditory threshold, the latter being correlated to hair cell function.