Room Acoustics

Reverberation Time, Speech Intelligibility, Background Noise

This page provides an overview on the subject of Room Acoustics. We cover the terminology and list the key measurements required to determine the acoustic properties of a room. We also provide links to how each actual measurement is done.

Room Acoustics is distinguishable from Building Acoustics, which essentially deals with the insulation of noise from other rooms or the outside world.

Understand the essentials: key terms and what they mean in real rooms (speech, music, comfort).
Know what to measure: Reverberation Time, Speech Intelligibility and Background Noise (Noise Curve).
Learn how it’s measured: links to the practical measurement workflows and required instruments.

What do Room Acoustic experts measure?

Room Acoustics is a broad term that describes the acoustic properties of closed spaces. Measuring and controlling this behavior of waves is particularly useful in rooms where the quality of announcement messages and/or music is important, such as in meeting rooms, conference halls, classrooms, concert halls, recording studios, airports, and train stations.

There are three main measurements that assist Room Acoustic experts in characterizing the acoustic properties of a room.

Why is it necessary to measure?

Rooms with too many or too few reflective surfaces, or too much or too little background noise can affect people’s moods and psyche.

Think of how cold and loud a conversation sounds in a hospital with tiled, reflective surfaces compared to how warm and soft a conversation sounds in a cinema with cushioned seats and walls (of course the purpose of the location has a significant effect on your mood too).

Think of how your mood changes in your office when a heavy construction machine starts up nearby. It is difficult to relax in such a space. Such unnatural-sounding rooms may also make speech difficult to understand, thereby affecting our ability and desire to communicate.

Every room needs to have the background noise under control to make the room fit-for-purpose.

The room should also respond acoustically with an appropriate amount of reverberation. For example, for good speech intelligibility in a classroom, the reverberation time should be around 1 second or less. A classical music concert hall, on the other hand, needs reverberation times of 2-3 seconds to ensure a rich and warm listening experience.

Which measurement instruments do you need?

The Room Acoustics Kit measures the behavior of acoustic sound in enclosed spaces, such as dwellings, class rooms, auditoriums, offices, theatres, concert halls, or transportation terminals. The kit consists of the DS3 Dodecahedron Speaker kit, the XL3 Acoustic Analyzer and the Room Acoustics Reporter software. All measurements are performed in accordance with the relevant standards.

Sound Level Meter

The Sound Level Meter measures all required data. These are the sound levels in the sending and the receiving room, the background noise and the reverberation time, which quantifies the room effect.
DS3 Dodecahedron Speaker Kit

The DS3 Dodecahedron Speaker, together with the PA3 Power Amplifier, meets all the requirements of the ISO 16283 standard. In addition, we offer impressive performance data; with a weight of only 7.5 kg and a typical sound power of 120.5 dB, the DS3 is convenient to carry around on site. By pressing a button on the supplied wireless remote control, the test signal can be comfortably switched on and off from outside the sending room.
TalkBox

The TalkBox is an acoustic signal generator. It provides a wide range of test signals like Sine, Pink Noise, White Noise, a delay test signal, and spoken announcements. It offers a balanced Line-In/Out connector and an FIR equalized speaker (level and phase).
Minirator MR-PRO

The Minirator MR-PRO generates a gated Pink Noise with a low Crest factor dedicated to Reverberation Time Measurements. In addition, the MR-PRO offers a GlideSweep signal with editable cycle time. All test signals may be replayed via the DS3 Dodecahedron Speaker kit.
Room Acoustics Reporter Software

The XL3 Acoustic Analyzer saves the acquired measurement data on its SD card. The data contains all relevant information formatted as a text file so it can be easily imported into any spreadsheet program such as MS Excel or the professional Room Acoustics Reporter software.

NTi Instruments at Work

Frequently Asked Questions

Can I control the XL3 remotely and download data without stopping a measurement?
Yes. The XL3 includes an integrated web server and file server for browser based control via Wi Fi or LAN, and measurement data can be downloaded while the measurement continues. XL3 can also be remotely used to perform Building Acoustics measurement using Sound Insulation Reporter Software.
How do I ensure accurate XL2 sound level measurements on site?
Use the XL2 with a suitable measurement microphone and perform a quick acoustic calibration with a sound calibrator (typically 94 dB at 1 kHz) before and after the measurement session. This creates traceable results and helps catch setup or microphone issues early.
Does the XL2 support STIPA speech intelligibility testing?
Yes. With the STIPA Option installed, the XL2 measures speech intelligibility according to IEC 60268-16:2020 (and also supports older editions), including features like ambient noise correction and automated averaging.