Principles of Building Acoustics

Building Acoustics Solutions

Building acoustics is a broad term that deals with sound transmission between adjacent rooms, or from the outside world. Building acousticians measure the effectiveness of a partition, such as a wall or ceiling, to insulate against external noise. This includes both airborne and impact noise.

Building Acoustics is distinguishable from Room Acoustics, which essentially deals with the acoustic properties within the room itself.


What do Building Acoustic experts measure?

Experts measure the sound insulation between two rooms. They do this by generating a sound in a room, and by comparing this sound level with the level that they measure in a, normally adjacent, room.

Airborne and impact noise are distinguished as follows.


Airborne noise is sound that is transmitted through the air, such as people talking in the room next door.

Impact noise results e.g. from footsteps on a floor, which can be heard in the room below.

Outside the USA, the Sound Reduction Index (SRI) is measured.

In the United States, the Sound Transmission Class (STC) rating is generally preferred.


The process of calculating the SRI or the STC may also require that the background noise and the Reverberation Time RT60 are measured.


How to measure airborne / impact sound insulation?

The measurement principle is simply to create a measured noise in the first room (the sending room) and compare that to a (potentially simultaneous) measurement in the second room (the receiving room).

Such an airborne sound insulation measurement quantifies the ability of the walls, floor, ceiling, windows, doors, or even ventilators to isolate noise between the sending and receiving rooms.

In some cases the "sending room" is not a room at all, rather the source is generated outside the building and measured through the facade in the receiving room situated inside the building.

In order to measure the airborne sound insulation, the determination of the background sound level as a single broadband value or several values across the frequency spectrum may be required.

Building Acoustics Airborne sound insulation measurement

Airborne sound insulation measurement

For impact sound insulation measurement (structure-borne noise), a calibrated Tapping Machine is used to generate the noise by knocking on the floor. (a calibrated rubber ball can also be used).

A sound level meter in the room below records the noise level and a PC-software calculates the desired results.

Depending on the standard, measurement of the reverberation time may also be required in determining the impact sound insulation.

Building Acoustics Impact sound insulation measurement

Impact sound insulation measurement


Which measurement instruments do you need?

You will need a Sound Level Meter that is capable of measuring the required aoustic parameters in accordance with the standards. You will also need a Dodecahedron Loudspeaker as a sound source for airborne sound insulation measurements, and a Tapping Machine to produce the impact sounds. Furthermore, using a professional software package for controlling the process and reporting the results may simplify the task.

1) Sound Level Meter

The XL2 Acoustic Analyzer is key to the building acoustics measurement kit. It is used to measure the levels, of the generated sound, in the sending and receiving rooms. The XL2 can be controlled remotely, enabling the Sound Insulation Reporter software to control the entire measurement process, by automatically acquiring, evaluating and reporting on the measurement data.

The robust housing makes your XL2 into a long-lasting partner.

  • Remote control
  • Shockproof
  • Type-Approved

Download XL2 Acoustic Analyzer Product Data

2) Dodecahedron Speaker

The ISO 16283 standard requires the use of an omni-directional loudspeaker for the measurement of airborne sound insulation. The loudspeaker produces a pink noise, while the sound level measurements take place in the sending and adjacent receiving room.

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 121 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.

  • Compact and lightweight 
  • Maximum sound power level 121 dB 
  • Wireless remote control

Download Dodecahedron Speaker Set Product Data

3) Tapping Machine

The TM3 Tapping Machine produces the impacts on the floor to determine the impact sound insulation. The hammers in this PTB-approved precision instrument hit the ground at a prescribed rate and with a constant, measured force. The remote-controlled TM3 is compliant with the standards that define building acoustics.

  • Standards-compliant
  • Wireless remote control

Download TM3 Tapping Machine Product Data

4) Reporting Software

FX100 Control Software

Last but not least, the measurement results obtained by the XL2 can be easily imported into the "Sound Insulation Reporter". This PC software then calculates the required results for the airborne and impact sound insulation in accordance with the selected standards.

During measurement, the Sound Insulation Reporter may provide direct remote control of two or more connected XL2 Acoustic Analyzers. Furthermore, it collects the data acquired by the XL2. This allows simultaneous measurement in the sending and receiving rooms, thus saving time.


  • Airborne, impact and facade sound insulation
  • Parallel measurements in sending and receiving room
  • Standardized Reporting

More about Sound Insulation Reporter

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5 reasons why the XL2 is the right choice for you

The XL2 Acoustic Analyzer offers all the measurement functions relevant to building acoustics in one instrument. Thanks to the intuitive operation, you can quickly and easily switch between the different measuring functions.

XL2 Acoustic Analyzer for Building Acoustics Measurements
XL2 Acoustic Analyzer for Building Acoustics Measurements

  • rugged and ready for tough building environments.
  • the XL2 automatically detects the sensitivity of the microphone for indisputable accuracy.
  • all measurement results are stored on a removable SD card as TXT files, which can be further processed externally with a PC or MAC.
  • besides the Building Acoustics measurements, the XL2 has many other expandable measurement functions. So, if you have other acoustic or audio measurement tasks, it's likely that the XL2 can help you.
  • Together with the Type Approval Option, the XL2 is an approved Sound Level Meter.


International Standards

Building Acoustics measurements are defined by international and national standards.

  • The optimized frequency response of the Dodecahedron Speaker Set ensures precise measurements in accordance with the ISO 16283 and the ISO 3382 standards.
  • The TM3 Tapping Machine is compliant to the standards ISO 16283-2, ISO 717-2, ISO 10140-3/-4/-5, ISO 140-6/-7/-8, DIN 52210-6, ASTM E492, ASTM E1007.
  • The Sound Insulation Reporter software adheres to the ISO 16283, ISO 140, ISO 717, ISO 10140, DIN 4109, Document E, ASTM E336, ASTM E413, ASTM E1007, ASTM E989, ASTM E966, ASTM E1332, GB/T 19889, and SIA 181 Standards.
  • The solution offered by NTi Audio is compliant with the ISO 16283, ISO 140 and ASTM E336 standards.


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