AES Vienna Video: NTI Talkbox Testing Speaker
Speech intelligibility testing is one of the businesses of NTI, makers of finely calibrated testing equipment for acousticians, sound systems integrators and designers. The NTI Talkbox is a handheld unit combining a speaker and a DSP/amplification unit. The purpose of the Talkbox is to deliver an extremely flat frequency response.
"Flatness" is a measure of fidelity to the input signal - the more flat a response is, the less exaggeration or reduction of any frequencies in the output signal as compared to the input signal are present. In speech intelligibility (or nearly any acoutsic testing), this is a much-needed feature. If your test source is coloring the test audio, then the test results are useless. Get a close look at the NTI Talkbox in this video shot live in 2007 from the floor of 122nd AES in Vienna, Austria.
THOMAS HUPP: NTI is also very an important player in measuring speech intelligibility. Speech intelligibility is important on railway stations or official buildings to make sure those emergency announcements are very good or very well understood. For these measurements, we need to replace a real speaker by a synthetic signal, which is the so-called STI-PA test signal.
This is a loudspeaker. The loudspeaker has to have very characteristics like a real human speaker has, so the directivity has to be in the same range and also it has to be very flat. For this, NTI offers the so-called Talkbox. The Talkbox is an active speaker. There’s a high-quality speaker in there and amplifier-DSP combination on the back side.
Each Talkbox is calibrated in a specially controlled acoustic environment with 15 measurements and then calibrated to get a very, very flat frequency response down to 0.5 dB or with a frequency range from 100 Hz to 10 kHz.
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