ANSI/ASA S1.13-2020 Measuring Sound Pressure Levels in Air

Red megaphone bursting subjective loudness, which can be properly measured with ANSI/ASA S1.13-2020 sound pressure levels.

Have you heard: the American National Standard ANSI/ASA S1.13-2020: Measurement Of Sound Pressure Levels In Air has been revised.

What is Loudness?

In the beginning, there was sound. Just after the Big Bang, the universe persisted as a thick, hot soup that trapped light. In the primordial darkness, if you pushed on a pocket of hot gas, it resisted and pushed back. The result was a dark early universe that rang with countless cosmic bells with ripples like the surface of a pond pummeled with stones. Once things settled down, these sound ripples accumulated extra matter, forming more galaxies than other spots in the young cradle of existence. Of course, the imprint of these early chaotic years of the universe has remained as the Cosmic Microwave Background, which can be heard while using appropriate equipment.

Sound is a pressure fluctuation in the air. We perceive many sounds as loud or louder than others, but loudness is a subjective measure. In general, the greater the amplitude of the pressure fluctuation in the air, the “louder” people perceive it.

Parameters of loudness vary from one person to the next. Sound pressure levels, however, are objective, and derive from the measurement of the amplitude of pressure fluctuations, which depends solely on physical parameters. With this, the measurements of sound captured with ANSI/ASA S1.13-2020 are not subject to interpretation or opinion, as opposed to the subjective characterization of loudness.

Why Measure Sound Pressure Levels?

Sound pressure measurements typically characterize either a source or an environment. With this, the reasons for measuring sound pressure levels are numerous, which, in turn, makes for a plentitude of applications of the ANSI/ASA S1.13-2020 standard.

For example, one could measure the sound pressure level at a certain point in or around the home, at a concert, or at a work environment. The standard can also help detect sound pressure at a certain point due to the switching on or off of a particular sound source or to assess hearing damage risk from noise exposure or compliance with regulations and particular specifications.

About ANSI/ASA S1.13-2020 Procedures

By establishing uniform procedures for measuring the sound pressure level in air at a single point in space, ANSI/ASA S1.13-2020 standardizes the basic requirements of sound pressure level measurements. This document covers the various types of sound, the types of acoustical environments, instrumentation for taking the measurements, the measurement processes, dealing with uncertainty, and documentation.

Colorful sound waves representing ANSI/ASA S1.13-2020 sound pressure level measurements.

The requirements and procedures outlined in ANSI/ASA S1.13-2020 apply primarily to measurements performed under normal, relatively quiescent meteorological conditions. Nearly all measurements made indoors will fall under such conditions, but outdoor measurements may apply if certain environmental conditions are met.

The type of sounds measured through this standard can vary greatly in temporal and spectral characteristics (being continuous or intermittent or steady or fluctuating), and the applications can fit a multitude of purposes. The frequency range covered in ANSI/ASA S1.13-2020 is also expansive, and it largely depends on the specific type of sound level meter or instrumentation used. The frequency content of the sound measured should be contained within the range from 20 Hz to 20 kHz.

Ultimately, the range of information covered in this standard helps make the procedures of acoustical measurements more accessible to practitioners in the field by clearly defining the steps and types of required instrumentation.

What ANSI/ASA S1.13-2020 Does Not Cover

ANSI/ASA S1.13-2020 does not include the measurement of:

  • Sounds whose duration is less than one second (impulsive sounds),
  • The spatial characteristics of the sound field,
  • Sound pressure levels in environments other than air (other gases, liquids, or solids),
  • Infrasonic or ultrasonic sounds,
  • Spatial characteristics of sound fields,
  • Sound pressure levels outdoors in nonquiescent conditions (generally).

Changes to ANSI/ASA S1.13-2020

In revising the 2005 edition of the same American National Standard for measuring sound pressure levels, ANSI/ASA S1.13-2020 underwent some editorial updates and saw changes to the references listed in the document.

This new edition was a limited revision developed by Accredited Standards Committee S1 Acoustics and saw two further notable changes. In paragraphs 8.3 through 8.6, the low frequency limit of 87.1 was added for several instrumentation types for measuring sound pressure levels. Furthermore, in Annex A, the threshold (quiet) criterion referenced is found in ECMA 74-2015, Annex D, 10.8 “Audibility Requirements.”

ANSI/ASA S1.13-2020: Measurement Of Sound Pressure Levels In Air is available on the ANSI Webstore.

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