Speech Intelligibility Meter with STIPA and Full STI


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SM50 Speech Intelligibility Meter

STIPA has become the industry standard for measuring the Speech Transmission Index. The Bedrock SM50 Speech Intelligibility Meter is the device that many have been waiting for, a high-end speech intelligibility meter that is accurate, reliable and affordable. This device was designed from scratch by the very team that invented STIPA.  Additionally, this same team was responsible for the development of the Speech Transmission Index for the last few decades.

SM50 and STI

With its full-color touch screen, the SM50 is easy to use and understand even to first-time users of the Speech Transmission Index. The casual STI user will not have to deal with impossible key combinations, complex calibration procedures and other discomforts that people have come to expect from STI measuring tools. Comparatively, the SM50 is easy to use, intuitive and almost plug-and-play. At the same time, even seasoned STI experts will find every feature they have ever wanted, including full STI testing using the direct method. As of our v2.0 software update, our speech intelligibility meter can now conduct full STI tests using the direct method in 65 seconds. This is a landmark in speech intelligibility testing!

The SM50 was designed from the ground up by the inventors of STIPA. Additionally, it is a fully compliant Speech Transmission Index measuring device as specified in IEC-60268-16 4th ed. (2011). It offers two STIPA measuring modes such as a quick screening mode, optimized for ease of use and for quick use, and a “Pro” mode that offers the most complete and versatile functionality of any STI measurement to date.

Furthermore, the SM50 is a fully compliant class 2 sound level meter and real-time analyzer. All functions featured on the Bedrock SM30 instrument are also included on the Bedrock SM50, perhaps making this the only acoustic measuring instrument you’ll ever need.

SM50 Speech Intelligibility Meter and BTB65 Talkbox


  • STIPA measuring with quick screening mode, pro mode, and averaging mode.
  • Full STI measurement using the direct method in 65 seconds. 
  • Speech Level Measurements cf IEC-60268 Annex J. 
  • Class 2 / Type 2 sound level meter with fast, slow, impulse; A/C.Z-weighting, Leq, and SEL.
  • Statistical acoustics – L10, L90, etc.
  • Real Time Analyzer – 1/12, 1/6, 1/3 and 1/1 octave.
  • FFT analyzer with detailed frequency analysis up to 32768 lines.
  • RT60 measuring- reverberation times: T20/T30/EDT.
  • Noise Curves – NR, NC, PNC, NCB, RC, RC mark II.
  • THD+N With firmware 2.6.
  • Fundamental frequency estimation With firmware 2.6.
  • Building acoustics: D, R’, DnT, Dn With firmware 2.6.
  • Building acoustics: SRI/STC. With firmware 2.6.
  • Audio oscilloscope.
  • Long term logging and monitoring – LEQ, RTA.
  • AC Volt meter for audio line level measurements – dBU, dBV, V rms.
  • Calibrated audio recording.
  • USB audio device mode – calibrated audio for your PC-based software applications.
  • More functionality will be added through free future firmware upgrades.


  • 20 – 20.000 Hz frequency range.
  • Dynamic range of 24-124 dB with included BAMT2 microphone.
  • Full-color resistive LCD touch screen with 240×230 px.
  • 4 GB of storage with at least 95% available for user data.
  • Access to stored data and recorded audio through high-speed USB 2.0 interface.
  • Integrated long-life battery pack, which is rechargeable via USB.
  • Complies with IEC 60268-16 rev. 4, IEC 61672 Class 2, ANSI S1.4 Type 2, IEC-62160 class 0 (RTA), and ISO-3382.
  • All necessary accessories, such as microphone, charger, cables, windscreen and carrying case are included in a ruggedized waterproof carrying case.
functions Real Time Analyzer (RTA) module on the SM50 Speech Intelligibility Meter