SM50 Sound Level Meter & STIPA Tester

 SM50 Sound Level Meter & STIPA Tester SM50(1) SM50(2) SM50(3) SM50(4) SM50(5)
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SM50 Sound Level Meter & STIPA Tester

The Bedrock SM50 Sound level Meter Class 2  from Bedrock is provides both Sound pressure level measurements (SPL) and is STIPA meter to measure Sound Transmission Index as STIPA- which is the industry standard. This Class 2 Data-Logging meter with certificate of conformity is an industry leading instrument in STI measurement for public announcement – which is mandated to be tested in rail, metro, airports, large conference rooms or any location with public announcement system to check the speech intelligibility of sound i.e., the ability for any person to clearly hear & understand announcements made on the PA or speaker system. 

SM50 STIPA meter is equipped with the following advanced modules:

  • Class 2 Sound Level Meter (SLM)


  • Real Time Analyzer (RTA)


  • Fast Fourier Transform (FFT) Analyzer

  • RTA Logging


  • RT60 Measuring (Reverberation Time)


  • Level (L%)


  • Noise Curve Analysis


  • Sound Pressure Level (SPL)


  • Total Harmonic Distortion plus Noise (THD+N)


  • LAeq logging


  • Statistical Acoustics and Building Acoustics SRI/STC


Equipped with a Class 2 electret microphone & preamp (1/4”), 30 mV/Pa sensitivity and a dynamic range of 21- 132 dB, this instrument gives accurate and reliable results in less time. With an easy plug-and-play method of operation and tripod mounted long term data logging, this class 2 stipa sound meter is perfect for longer duration of sound measurement. This data can be stored in the 4 GB internal storage or send to PC as .csv files for data viewing in spreadsheets; audio recordings also saved in .csv files.


SM50 is a STIPA sound meter that is accurate, reliable, and easy to use for even first-time users of STI measurement. Equipped with Quick STIPA (~18s per reading) as well as STIPA Pro (~25s per reading), even seasoned STI users will find all the features they were looking for- in a much simpler format in this speech intelligibility meter.



STI averaging available in SM50 Sound level & STIPA meter does multiple STIPA measurements consecutively and take a (moving) average across up to five measured STI values.

STIPA pro module has five screens:

1. STI and spectrum: display measured STI, octave spectrum and dBA level 2.


2. Measurement details: display all measurement details including the MTF

3. Settings: configure the STIPA pro module.

4. Additive noise: enter and enable/disable a noise spectrum to add to data

5. Browse measurements: review saved measurements


These measurement details will enable more experienced operators to determine not only the speech intelligibility of the tested channel, but also the causes of intelligibility reduction induced by the channel.


Full STI

Although fast and robust, STIPA has its limitations: only 2 modulation frequencies are measured per octave band, whereas the complete Speech Transmission Index measurement scheme calls for 14 modulations per octave band. This means that STIPA is under sampled in the modulation domain. For many systems, the measured STI is not (or hardly) affected. However, some cases call for “Full STI” measurements:

  • Whenever echoes are present (delayed loudspeakers, large halls and cathedrals)
  • When tested systems or channels feature complex combinations of distortion factors.

The Full STI module implements a novel measurement algorithm, that leverages the advanced signal processing capabilities of the SM50.

  • A novel test signal is used, which repeats 7 different patterns (segments) in a circular fashion.
  • Each pattern roughly follows the approach of STIPA: each octave band is simultaneously modulated with 2 modulation frequencies.
  • Each pattern takes approx. 9 seconds to complete. The whole measurement is completed in 65 seconds.
  • The patterns are set up in such a way that all modulation frequencies (out of the set of 14) have been used in each octave band once the full 65 second        cycle is completed. Hence, all 14 modulation frequencies are tested in all 7 octave bands.
  • The first phase of a new measurement is a synchronization phase, during which the analysis algorithm determines when to expect transitions between patterns. 


Bedrock SM50 advanced sound level meters with their versatile interface & tripod mounted setup can be are used for a variety of measurement applications including environmental noise, noise pollution, vehicular noise equipment & automotive design noise measurements, R&D, building acoustics, sound insulation, acoustic equipment testing, audio professionals amongst other applications. 

Conforms to major international standards like:

  • IEC-60268-16 rev. 4 & rev. 5
  • IEC-61672 Class 2 / ANSI S1.4 Type 2
  • IEC-61260 Class 0
  • ISO-717-1 / ISO-16283 / ISO-140
  • ASTM E336 / ASTM E413 ISO-3382-2
  • ANSI S12.2 / ISO-1996 AES17

Each SM50 speech intelligibility meter comes with an individual declaration of conformity and calibration certificate to differentiate the instrument from market variants. They also come with more functionality which will be added through free future firmware upgrades.

The SM50 is a versatile multi-point STIPA meter perfect for sound analysis and STI measurement – either tripod mount or handheld.


Kit Contains:

  • SM50 Instrument with class 2 mic
  • International charger adaptor
  • USB cable
  • Windscreen
  • Carrying cord
  • User manual
  • Calibration certificate
  • Ruggedized Case

The SM50 when combined with BTB65 Talkbox (available as Speech Intelligibility Kit) can be used to effectively measure STIPA- wherein the Talkbox acts as the source of STIPA signals and the SM50 measures/ analyses the signals seamlessly enabling multiple point testing in a short time with highest level of accuracy.

Optional BAC2 Calibrator is available to verify and calibrate the SM50. Provided with individual calibration certificate.

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SM50 Sound Level Meter & STIPA Tester
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