Brüel & Kjær Launches Wireless Echo Speech Sound Source

Performing speech intelligibility measurements is quicker and easier with Bruel & Kjaer's new, battery-powered speech sound source.

Used in combination with the DIRAC 6 room acoustics software, the new Echo Speech Source Type 4720 enables users to perform speech intelligibility measurements, which meet standards IEC 60268-16 and ISO 3382-3 (open plan offices).

The echo speech source works as a standalone tool with five in-built calibrated signals, which are used by the DIRAC room acoustics software to calculate a range of speech intelligibility parameters, such as STI, STIPA and RASTI based on the impulse response of the room being measured.

Users can measure the speech intelligibility of a sound reinforcement system using an excitation signal, played directly from DIRAC, through the sound device output or from an external device such as a CD or MP3 player.

The Echo/DIRAC combination copes well with high levels of background noise, as the echo speech source uses an intermittent stimulus. The intermittent stimulus consists of a Maximum Length Sequence (MLS) sequence followed by an equally long period of silence. The full stimulus (MLS and silence) is measured in one go. DIRAC then extracts the impulse response and the background noise into two separate channels of a .wav file.

DIRAC is a valuable tool for field and laboratory acoustics engineers interested in measuring room acoustics - and also for researchers and educational institutions. As well as measuring acoustics within any room or space, users can make comparisons between one room and another, validate sound systems and perform scale model measurements.

More information is available on Bruel & Kjaer's website.


About Brüel & Kjær
Brüel & Kjær is a world-leading manufacturer and supplier of sound and vibration measurement systems.
We help customers measure and manage the quality of sound and vibration in their products and in the environment. Focus areas include aerospace, space, defence, automotive, ground transportation, airport environment, urban environment, telecom and audio.

Our portfolio of sound and vibration equipment includes sound level meters, microphones, accelerometers, conditioning amplifiers, calibrators, noise and vibration analysers and PULSE software.
We also design and manufacture the LDS range of vibration test systems, as well as complete airport and environmental monitoring systems: WebTrak, ANOMS, NoiseOffice and Noise Sentinel.
To see our full range of solutions, systems and products, please visit:

We run a variety of training courses, from basic introductions on noise and its effects, to more specialised classes teaching customers how to get the most out of their equipment.
Free, online training courses - conducted by our expert engineers - run throughout the year. For all course registration details, please visit:

Brüel & Kjær is a subsidiary of UK-based Spectris plc ( which has annual sales of £1.1bn and employs around 7,500 people worldwide across its four business segments.

For additional information please contact:
Heather Wilkins
Marketing Coordinator
Bruel & Kjaer
Telephone: 01223 389 800