This technical specification applies to the specification and evaluation of outdoor audible noise from high voltage direct current (HVDC) substations. It is intended to be primarily for the use of the utilities and consultants who are responsible for issuing technical specifications for new HVDC projects with and evaluating designs proposed by prospective contractors. It is primarily intended for HVDC projects with line-commutated converters. Part of this technical specification can also be used for the same purpose for HVDC projects using voltage sourced converters, and for flexible a.c. transmission systems (FACTS) devices such as static Var compensators (SVCs) and static synchronous compensators (STATCOMs).Cross References:ISO 3743-2:2018ISO 3744ISO 8297ISO 3746IEC 61672-2ISO 9613-2ISO 9614-2IEC 60076-10-1ISO 3745ISO 9614-1ISO 9613-1IEC 61672-1IEC 60076-10ISO 3740ISO 1996-2:2017ISO 266:1997IEEE Std C57.136:2000IEEE Std 1127:1998IEEE C37.082:1982ANSI S1.11: 2004CIGRE Report 14.26Incorporates the following:Amendment, May 2019