NTI Audio Talkbox

The NTI Audio Talkbox simulates a human talker (60 dBA @ 1 meter according to IEC 60268-16) with the STIPA test signal and spoken messages. Further it provides a wide range of test signals like sine, pink noise, white noise and delay. It offers a balanced line In/Out connector and a FIR equalized speaker (level and phase).

The NTI Audio Talkbox features human head-like dimensions and is based on a solid-state-generator. It replays the STIPA test signal at the precisely equalized frequency response, also ensuring best performance through the internal amplifier and the precision loudspeaker. A variety of supplied or user-defined test signals may be used for different alignment applications.

The NTI Audio Talkbox has been designed to latest quality standards for reliable measurements results. It offers unmatched signal purity with a minimum distortion over the complete frequency range from 100 Hz to 10 kHz. This ensures the repeatable and precise verification of the speech intelligibility STI.

The NTi Audio TalkBox includes a high-precision broadband loudspeaker, with characteristic little distortion even at low frequencies. Perfect flatness of ±1 dB over the relevant frequency range and highest quality requirements are guaranteed by an individual equalization and calibration using advanced FIR filtering and DSP technology. The radiation characteristic corresponds broadly to the human mouth as defined in the ITU-T P.51 standard.

The IEC 60268-16 standard specifies a sound pressure level for a speaker simulator of 60 dBA at a distance of 1 meter. The NTI Audio Talkbox output is fixed at these levels to comply with this standard. Thus the TalkBox has no volume control.

In an emergency situation, the person making the announcements will tend to talk louder. This is known as the Lombard Effect. The system must be tested at this increased level. All TalkBox STIPA-related signals are thus additionally available at a level of 70 dBA at a distance of 1 meter.

Using the balanced line output, the TalkBox can also be operated as an audio signal generator. Frequency deviations while sampling – a dangerous trap when using portable CD players for STIPA measurements – are completely eliminated.

Further, any external signal can be connected to the system using the balanced line input. The applied signal is seamlessly looped to the line output and simultaneously processed in the internal DSP in real-time and played through the speaker.

The NTI Audio Talkbox also generates additional test signals: a reference spoken sentence, white noise, pink noise, 1 kHz sine wave and the chirp for delay time measurement. Custom-designed signals may be loaded onto the CF Card and are seamlessly looped.

Typically the NTi Audio TalkBox is positioned on a conventional mic stand in front of the talker’s microphone; exactly at the position of the actual talking person during the announcements. For this purpose there is a tripod mount on the bottom plate of the TalkBox.

For measuring speech intelligibility in large buildings the remote mute functionality of the TalkBox is of great help. Any external switching device may be connected to the mute input, allowing e.g. a mobile phone to control ON/OFF functionality. Thus the STIPA test signal might be muted between measurements.