Reverberation Time Sound Level Meter

Measure RT60 Room Acoustic Parameters | Model 831C-RA

Reverberation time is a key parameter for characterizing the acoustic nature of a room. Reverberation time is defined as the time after the source of the sound has ceased that it takes the sound to fade away. The optimum reverberation time for a space depends on the space’s use, with longer reverberation time considered better for music and a shorter better for understanding speech.

SoundAdvisor™ Sound Level Meter Model 831C-RA, designed with simplicity in mind, offers reverberation time measurement tools compliant with the latest measurement standards for measurement of room acoustics, including ISO 3382-1, ISO 3382-2 and ASTM E2235-04.


  • Calculates reverberation time (RT60)
  • Ensures measurement reliability with ensemble averaging
  • Serves as pink and white noise source
  • Supports optional amplifiers and omni-directional or façade speakers
  • Triggers measurement automatically
  • 1/1 and 1/3 octave filters supported
  • Offers measurement quality indicators and grading


  • Architectural acoustics
  • Room acoustics
  • Acoustic absorption materials testing
  • Reverberation time
  • Performance space acoustics
  • Classroom acoustics

Visualize Room Acoustic Data

Use the included G4 LD Software to visualize reverberation time and room acoustics data. Easily export data to create shareable reports. Measurements are reviewed quickly and easily to identify any questionable decays and exclude them from the final results. RT60 decay times are displayed using both the T20 and T30 computation methods, and reporting includes associated quality indicators.

Want to be more mobile? Wirelessly control reverberation time measurements and view real time results using the LD Atlas app, available for Android and iOS.

Already own a SoundAdvisor Sound Level Meter or System? Add room acoustic tools to your Sound Level Meter without returning it to the factory by adding Model 831C-RA Firmware. Contact our team to learn more.

RT60 Decay Curve Display

Room Acoustics Measurement Quality Indicators

Built-In Noise Source

RT60 Spectra Display

Room Acoustics Measurement Grading

RT60 Decay Using Interrupted Noise Method

831C-RT Specifications
831C-RT Complies with the Following Standards
ISO 3382-1:2009Acoustics — Measurement of room acoustic parameters — Part 1: Performance spaces
ISO 3382-2:2008Acoustics — Measurement of room acoustic parameters — Part 2: Reverberation time in ordinary rooms
ASTM E2235-04Standard Test Method for Determination of Decay Rates for Use in Sound Insulation Test Methods
IEC 61672-1:2002Class 1 Electroacoustics – Sound level meters
IEC 61260-1:2003Class 0 Electroacoustics – Octave-band and fractional-octave-band filters
Reverberation Time
Calculation Methods AvailableImpulse excitation using reverse time integration (Schroeder method)
Interrupted noise excitation with internal or external source
T20 and T30 slope calculationLeast squares estimation
1/1 octave band63Hz to 8 000 Hz
1/3 octave band 50 Hz to 10 000 Hz
Selectable bandwidth(1/1 or 1/3 octave) and selectable frequency range
Trigger bandwidth and levelSelectable
Programmable exit time0 to 99 seconds
Programmable build time (interrupted noise method)0 to 19 seconds
Programmable acquisition time2 to 9 seconds
Sampling time2.5, 5, 10, or 20 milliseconds
Reverberation timeAs large as 33 s (19 s acquisition window, with 20 ms sample time)
Measurement stateExit, background, pretrigger, ready, triggered, done
Decay viewingEnsemble and individual
Predefined setups availableImpulse and interrupted noise methods
Data viewing optionsDecay exclude and include
Reverberation time spectraT20 and T30
Quality Indicators to ISO 3382-2
Measured parametersCurvature, standard deviation, non-linearity, BT check, and SNR-background
Quality indicator optionsEnsemble or individual decay
Uncertainty grade indicatorSurvey, engineering, or precision
On-board Signal Generator
Noise generationPink or white noise with 0 to 50 dB attenuation in 3 dB steps
Generator output2.5 mm jack
Preview modeMeasurement controlled or manual
Data Management
Storage of data on SoundAdvisor™ with or without individual decays
Data export to SLM Utility Software, MS Excel, DNA, and Larson Davis SDK
Sound Level Meter
Requires no other software option
Field upgradable

Learn more about Reverberation Time measurements and calculations.