Challenges of acoustic measurements in performance sites

Challenges of acoustic measurements in performance sites

By In Uncategorized On March 16, 2021

Why a monopole sound source outperforms dodecahedron loudspeakers

Room acoustic measurements in performance sites

A monopole omni-directional sound source will provide the most accurate room acoustic measurements. These can be applied to any type of closed or semi-closed space (e.g. office spaces, apartment buildings) but bove all, this level of accuracy is most interesting for measurements in theaters, churches, opera houses and concert halls. When conducting measurements in performance sites, monopole sound sources outperform dodecahedron loudspeakers.

Its a real challenge to take measurements inside performance sites where control of sound quality and intelligibility are crucial factors.

These type of room acoustic measurements include:

  • Room Impulse Responses
  • Reverberation Time
  • Speech Transfer Measurements

Issues with standard omni-directional speakers

Studies* show that in the frequency bands ranging from 125Hz. to 1kHz. octaves, all types of omni-directional sound sources can be used. However, above 1kHz. measurements might be afflicted by using for instance a 12-speaker dodecahedron sound source.

The solution

Qsources Qoms2 is monopole omni-directional source which include 2 unique Qsources QP4 drivers.
This small & lightweight source is powerful enough for measurements in any type of performance site. In addition, it’s suitable for broadband measurements in wide frequency range (1/3 octaves: 50-16000 kHz.). Next to the output benefits, the light weight (1.25 kg) and the small dimensions (10.6cm) diameter allow this sound source and its measurement amplifier (Qam or Qca) to be taken on site and set up in a stress free and fast manner.

The Qoms2 speaker is designed to conform to amongst other ISO 140, ISO 3382, ISO 16283 and 14275.

The below images show why the measurements of Qoms2 are more precise than standard omni-directional speakers or dodecahedrons on the market.

When measured in tangential direction, the radial pattern showcases nearly perfect omni-directionality.

In axial position, the directivity is nearly perfect up to 4 kHz. & remains smooth, spherical and balanced in the highest octave bands up to 16 kHz.


In summary, the above results would be impossible to achieve using a standard omni-directional loudspeaker given these will show aspherical patterns above the frequency level of 1kHz. The Qoms2 monopole sound source outperforms dodecahedron loudspeakers.

*Relevant studies include:
Influence of loudspeaker directivity on the measurement uncertainty of the acoustic testing of facades. (Pedrero, Sanchez, Ulin & Diaz; 2011)
Uncertainties caused by source directivity in room-acoustic investigations (San Martin & Arana, 2008)
Uncertainties in measurement of single number parameters in room acoustics (Witew, Behler; 2005)