Brüel & Kjær - Model Type 4720 -Echo Speech Source
The Echo Speech Source features five different built-in and calibrated signals that are used by the DIRAC room acoustics software to calculate a range of speech intelligibility parameters.
In combination with DIRAC 6 the Echo Speech Source Type 4720 performs speech intelligibility measurements in accordance with IEC 60268-16 and ISO 3382-3 (open plan offices) quickly and easily.
To measure the speech intelligibility through a sound reinforcement system, you can use the loudspeakers of that system, and obtain the excitation signal directly from DIRAC through the sound device output or from an external device such as a CD or MP3 player.
The Echo / DIRAC combination also performs well with high levels of background noise. The Echo Speech Source can produce an intermittent stimulus. With the standard impulse response technique it is difficult to measure a high quality impulse response and at the same time retrieve an accurate background noise level from this measurement.
The intermittent stimulus consists of an MLS sequence followed by an equally long period of silence. The full stimulus (MLS + silence) is measured in one pass, and Dirac extracts the impulse response and the background noise into two separate channels of a .wav file.
This stimulus allows you to increase the output level and perform pre-averaging to improve the INR of the impulse response in speech intelligibility measurements, while still retaining accurate noise values.
In combination with DIRAC 6, the Echo Speech Source Type 4720 offers quick and easy measurement of speech intelligibility. Impulse response and background noise are measured in one pass using intermittent stimulus, i.e. MLS (Maximum Length Sequence) followed by an equally long period of silence.
Sound source delivering a calibrated signal that is used by the DIRAC room acoustics software to measure a range of speech intelligibility parameters.
In combination with DIRAC 6, the Echo Speech Source Type 4720 performs speech intelligibility measurements in accordance with IEC 60268-16 quickly and easily.
- Speech intelligibility measurements with DIRAC
- Measurements including background noise
- Wireless sound source for DIRAC 6
- Calibrated speech levels and spectra
- Mouth directivity
- Five built-in stimulus signals
- Intermittent stimulus accounting for background noise
- External input and output
- Compact and lightweight (10x10x17 cm, 1 kg)
- Mounts on standard tripods
- Battery powered
- External power supply included
With a calibrated speech source there is no need for external equalisers or speech level adjustment.
The signal can be set at an elevated level, making STI measurements possible even if the background noise is significant. DIRAC 6 recognises the output level and corrects calculations appropriately.
Adjust Volume of PA Systems
Echo Speech Source can be used to set the volume of PA systems using a male speech signal with a standard level of 60 dB(A).
Less Intrusive with MLS
For STI measurements, Echo Speech Source contains pink MLS signals. The MLS is far less intrusive than an e-sweep signal.
DIRAC is able to handle asynchronous MLS signals, allowing it to work with the Echo Speech Source (as well as CD and MP3 players).
