The intelligibility of speech in schools is an important part of successful learning. According to the ANC (Association of Noise Consultants), the typical speech level for a teacher in the classroom (at 66.5 dB) is higher than the normal speaking level. For this reason, NTi Audio now offers the speech intelligibility test signal for the TalkBox at this level. This is a free product upgrade for all TalkBox users.
In classrooms, windows and smooth surfaces, such as walls, ceilings and tables, reflect the spoken word. These hard surfaces reverberate the sound, and may reduce the intelligibility of the speech. As a result, the students have to be more concentrated to follow the lessons presented by the teacher. Over a longer period of time, this can lead to listener fatigue and consequently compromise the success of the study effort. Therefore, good speech intelligibility in classrooms is an essential goal of every school.
XL2 and TalkBox forms dedicated Test Kit
The NTi Audio TalkBox together with the XL2 Sound Level Meter is the measurment system for a fast, reliable determination of speech intelligibility in classrooms. The TalkBox acts as an acoustic reference sound source simulating the teacher’s voice. Positioned at the teacher’s normal speaking place, it emits a standardized test signal according to IEC 60268-16. At the pupils’ desks, the XL2 determines the Speech Transmission Index (STI) within a range of 0 to 1; 1 being the perfect value. The measurement is performed at several typical student positions in the classroom. The result represents objectively the intelligibility of the teacher’s speech. According to the British BB93 guidance, a value of at least 0.60 STI has to be achieved.
STIPA Test Signal with 60 and 66.5 dB available
The spoken level for speech intelligibility measurements is standardized at 60 dB, measured at a distance of one meter. This represents, for example, communication of students among themselves. On the other hand, the ANC reports that teachers typically present at an average spoken level of 66.5 dB. Teachers speak louder to be heard more clearly. To objectively measure the speech intelligibility NTi Audio now offers the TalkBox STIPA test signal with the recommended level of 66.5 dB. Further test signals, such as pink noise and voice recordings for plausibility checks are also included.
Unmatched Signal Quality with TalkBox
The TalkBox also simulates a human talker (60 dB @ 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. The TalkBox features human head-like dimensions and is based on a solid-state generator. It replays the STIPA test signal with a 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 TalkBox has been designed to the latest quality standards for reliable measurement results. It offers unmatched signal purity with a minimum distortion over the complete frequency range from 100 Hz to 10 kHz. This ensures repeatable and precise verification of the speech intelligibility STI.
The new 66.5 dB test signals for classroom applications are freely available for all registered TalkBox users. All XL2 Sound Level Meters can be extended with the speech intelligibility measurement option.
Speech Intelligibility Measurements
Download new Test Signals for TalkBox
Press Picture(s) for download here.