Items of interest and recent work
ECMA-425 specifies a statistical background correction (SBC) for removing background noise contributions from measured noise levels. Because background noise is present during source measurements, the measured levels include both source and background contributions. To isolate the source, the background is estimated from measurements taken when the source is not operating. However, as background noise fluctuations increase, accurately estimating the background and correcting the measured source levels becomes more difficult.
ECMA-74 specifies procedures for measuring and reporting the noise emission of information technology and telecommunications (ITT) equipment. The 22nd edition was updated to refer to ISO 26101-1 and -2 on acoustic environment qualification for sound power measurement instead of ISO 3744 and ISO 3745 and to allow such qualification in addition to that of ISO 11201 for sound pressure measurement. Revisions for consistent terminology between ECMA-74 and these standards were also made.
Future revisions to ECMA-74 will introduce a cylindrical microphone array angle error correction, allow application of the statistical background correction, and address time-varying noise emissions and composite rack equipment noise obtained from component measurements. Noise measurement procedures are also expected for IT equipment categories like JBODs (just a bunch of disks) arrays, tape storage robots, and quantum computers.
ECMA-109 specifies how to declare noise emissions of ITT equipment. The 11th edition contains revisions for declaring equipment whose noise emissions change with environmental temperature and altitude conditions and prescribes sound power declaration in terms of decibels (dB) instead of Bels (B).
ECMA-418 describes psychoacoustic metrics for ITT equipment and includes Part 1 (prominent discrete tones) and Part 2 (methods for describing human perception based on the Sottek Hearing Model). Future revisions to Part 1 will include a revised tone-to-noise ratio (TNR) procedure that excludes certain so-called secondary tones within the critical band containing the primary tone, for improved measurement repeatability. Future revisions to Part 2 will include a procedure for fluctuation strength measurement.
Task Group TG1 focuses on measurement of noise, vibration, and tonality of small air-moving devices and is developing a measurement procedure for fan testing with optional application of airflow resistance (by the ISO 10302 plenum) and optional representation of nearby structures affecting noise generation.
Task Group TG2 focuses on noise measurement of multi-function printers and related printing and imaging equipment.
Task Group TG3 focuses on psychoacoustic metrics applicable to ITT equipment and is working on increasing the accuracy and scope of metrics that describe noise perception using specialized sound signal processing.
Task Group TG4 focuses on noise measurement of rack-mounted equipment and is working on measurement procedures that address the various types, operating modes, and workloads of rack-mounted equipment, which is proliferating and moving into office spaces. TG4 is in the process of developing methods to identify and command the system resources of rack-mounted equipment for noise emission measurements.
Task Group TG5 focuses on modular acoustic data acquisition systems and is working on the requirements and procedures by which certification of data acquisition modules is established and maintained.
Task Group TG6 focuses on the air- and structure-borne noise that can degrade Hard Disk Drive (HDD) function and is working on procedures for measuring these noise disturbances.
TC26 maintains liaison with ISO TC43/SC1/WG23 (IT noise) and ISO TC43/SC1/WG28 (Noise emission from all types of equipment), and collaborates with the Open Compute Project (OCP HDD Dynamics). Through these liaisons and collaborations, TC26 can contribute to ISO/IEC standards that affect IT product noise measurements.
Please find below 2 video clips made during the TC26 meeting in Portland (23-24 July 2011); the first one is an interview of Dr. Robert Lotz (past TC26 Chair) and the second one is an interview of Dr. E. K. Dunens (past TC26 Chair).