Sound Level Meter & STIPA Tester

Sound Level Meter & STIPA Tester

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SMxx Series Sound Level Meters manufactured by Bedrock, NL- the inventors of STIPA and are state-of-the-art acoustic measuring equipment with the highest quality and reliability. Stanlay bring to market three distinct models- SM30, SM50 (Class 2 variants) and SM90 (Class 1 variant) sharing the same basic hardware platform and having the same intuitive user interface, but are each optimized for a different set of demands and applications.

Why Measure Sound Levels?

Sound level measurements can be categories in two parts  :  Sound Pressure level measurements (SPL) also referred to as Sound level meter (SLM) and STIPA i.e Speech Transmission Index for Public Address Systems.


Sound Level/ STIPA- STI is mandated to be tested in rail, metro, airports, large conference rooms or any location with public announcement system where it is necessary to check the speech intelligibility of sound heard by persons i.e., the ability for any person to clearly hear & understand announcements made on the PA or speaker system.


SPL or SLM noise level monitoring measurements find a wide array of application including:

  • environmental science
  • equipment, vessel, and automotive research & design
  • wide gamut of industrial & environmental noise pollution measurements including vehicular traffic noise
  • industrial noise pollution study
  • Building acoustics
  • sound insulation
  • acoustic equipment testing and audio professionals

  among many other applications.



All Bedrock handheld sound level meters have 20- 20,000 KHz frequency range with a 24-124 dB Dynamic Range (with included BAMT2 microphone) covering all the applications where sound level monitoring is required. The Full-color resistive LCD touch screen and high speed USB2.0 output interface make it easy to use for anybody involved in (acoustic) testing and certification.


All the sound level meters with data logger come with their individual declaration of conformity and calibration certificate to differentiate the instrument from market variants. The instrument will receive free future firmware upgrades for more functionality.


For versatile and long-term measurements- the SMxx sound meters are equipped with a tripod mounted facility with 5~8 hr. battery backup – facilitating long term sound monitoring.


Sound pressure level & spectrum measurements:

SMxx Series Bedrock  Sound Level Meters can measure:

  • Frequency Weighting (A: weighted, C: weighted, Z: Unweighted),
  • Time Weighting (Fast, Slow & Impulse),
  • Equivalent Continuous (EQ),
  • Sound Exposure Level (SEL),
  • Peak Values (PK) and
  • Various Room Acoustic Measurements.


Apart from these, the SMxx Digital sound level meters have modules to measure:

  • LAEQ- for long term monitoring and logging applications


  • RTA- for frequency analysis in range 20Hz- 20kHz


  • FFT- for spectral analysis & harmonics analysis of sound


  • L%- for statistical distribution of sound levels in measurement period


  • RTA Logging – for long term monitoring of spectral characteristics (1-999sec)



STIPA Measurement

The SM50 and SM90 Noise level meters are also STIPA meters to measure Sound Transmission Index (STI) as STIPA- which is the industry standard. 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 instrument.

Every STIPA measurement requires a source for the STIPA test signal. In the Speech intelligibility test, the Talkbox BTB65 due to its integrated loudspeaker, is used as the source of sound mimicking all the frequencies/modulations used in a normal speech. SM50/SM90 Digital sound level meter is then used to analyze the signal received and calculate the STI- giving a measure of how much of the speech is understandable. Due to its compact size and interactive LCD touchscreen, the BTB65 Talkbox is perfect for easy STIPA measurement at various points.

The SM50 or SM90 instrument with BTB65 Talkbox provides speech intelligibility measurements (available as a separate speech intelligibility kit) using the STIPA method according to most national and international standards, including the following:

  • NFPA72 Annex D
  • NEN2575
  • DIN-60849/DIN-VDE-0833-4
  • BS-5839-8
  • IEC-60268-16
  • ISO-7240-19


Optional Accessory:

BACx Acoustic Calibrators are optional accessories with the sound meter kits – used to verify the calibration of the instrument and adjust if required. We offer two options- BAC1 and BC2 (for Class 1 & Class 2 respectively)


Function Guideline / Application SM30 SM50 SM90
Modules / Functions
Sound Pressure Level Meter (SPL / SLM) IEC-61672-1 : 2014, ANSI S1.4,    Class 2 / Type 2 Class 2 / Type 2 Class 1 / Type 1
Frequency Weighting Choose frequency method A ,C, Z (A : weighted, C : weighted , Z : Unweighted)
Time Weighting Choose based on time frames FAST , Slow, Impulse
Equivalent continuous (EQ)   Computes the time-integrated level over the
measurement interval
Sound Exposure level (SEL)   Time-integrated value normalized to 1 sec
Peak Value   Highest instantaneous value within an interval
Max Hold Lock on highest values measured Maximum level during the measurement
interval; Used with Fast, Slow or Impulse time weighting
Measurement Time  Set duration of measurement Set Measurement Time or Continuous (for infinite)
LEQ Long-term  logging/monitoring (LAEQ) Monitoring of continuous environmental noise / logging of sound levels, e.g. LAeq15min Track equivalent continuous sound pressure level  (LEQ) develop over time with simultaneous logging of A/C/Z
Real Time Analyzer (RTA)  Frequency Analysis for separate frequency bands Frequency analysis in range 20 Hz to 20 KHz for frequency bands 1/1, 1/3, 1/6 or 1/2 octaves. Two spectral views present- frequency weighting or time weighting
Fast Fourier  Transform Analyzer (FFT) Perform spectral analysis with higher frequency resolution  Up to 32768 data points, with Zoom In/Out feature, Spectral analysis for identifying exact frequency and level of signal components and study of harmonic structure of sound
L%, Statistical acoustics  Acoustic statistics based on threshold expressed as percentile, e.g. L10 to L95 can be measured Simultaneous measurement and display of six different settings
RTA Logging Long term monitoring of special characteristics of sounds  Spectrograms, with averaging window between 1 to 999 seconds of spectrum in 1/1, 1/2, 1/6 or 1/12 octave as well as A, C , Z weighted equivalent continuous levels
Electro-Acoustics & Electric Analysis
Digital Storage Oscilloscope  Inspect acoustic signals, in particular periodic signals, in time domain Yes, up to 20kHz
Polarity  Check polarity of loudspeakers Yes,  Use test signals provided or use with BTB65 Talkbox
AC Volt Meter for Line Level Signals Assess Output level Yes, Measure Vrms, dBU, dBV
Total Harmonic Distortion & Noise (THD+N ) Quantify distortion levels in electro-acoustic equipment.   Value THD+N is expressed as a percentage (%) or a signal-to-noise ratio (dB)
Fundamental Frequency Estimation   Yes, Measurement in Hz with pitch & offset
Building / Structural Acoustics
Sound Insulation: Evaluate airborne sound transmission loss 4 different frequency dependent measures :  D, Dn, DnT, R
Sound Reduction Index; Sound Transm. Class (SRI / STC ) For specifying and measuring sound insulation   4 metrics R'w ;  Dn,w ; DnT,w ; STC
Room Acoustics
Reverberation Time (RT60) Measure sound energy decay Full Octave and 1/3rd octave measurements are supported. As per ISO-3382, Suggested to be used with BTB65 Talkbox
Noise Curves  Choose method based on standard. NR, NC, PNC, NCB, RC, RCII
Speech Intelligibility Test (STI) Measurement
Basic Intelligibility Measurements (Quick STIPA) For Public address systems, quick measurement in 18 secs No Yes
Advanced Intelligibility Measurements (STIPA Pro) For Public address systems, measure in 25 secs No Yes, with capability to enable/disable additive noise 
Full STI (IEC-60268-16) Most reliable complete STI measurement in 65 secs No Yes, 14 Modulation frequencies tested in 7 Octaves
Speech Level Meter   No Yes, (CF. 602168-16)
Qualification Band Shown   No A (Excellent) to U(Bad)
Acoustic Specifications
Linear Range, Electric Input (dBuV)   21 ~132dB 21 ~132dB 21-132 (expandable to 145 with attenuator)
Measurement Range (dB) , Linear Range with Supplied Microphone, dBA SPL   30 ~122dB 30 ~122dB 25-130 (expandable to 145 with attenuator)
Frequency Range (Hz) Covers entire range  heard by human ear 20 ~20.000
Accuracy (dB)   0.5 0.1
Resolution (dB)   0.1
Octave Filter   Class 1 1/1, 1/3, 1/6 and 1/12 octave filters
  31.5 Hz, 63 Hz, 125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, 8 kHz, 16 kHz
Analysis Rate   93.5 times/sec
Sampling Frequency (kHz)   48
Add Text Annotations to Measurements Yes 
Capability to Record Audio of all Measurements Yes, in .wav format
Automatic Level Calibration Procedure   Yes
Calibrated Recording of Audio on Internal Memory   Yes
Real-time Calibrated USB Audio Device Mode   Yes
Declaration of Conformity   Declaration of conformity provided with individual Calibration certificate 
External Calibrator   Optionally available
Display   Full-color 3.2” resistive LCD touchscreen display
Microphone Connector   XLR 48V
Microphone Provided with Instrument   Class 2 electret microphone & preamp (1/4”), 30 mV/Pa sensitivity Class 2 electret microphone & preamp (1/4”), 30 mV/Pa sensitivity Class 1 microphone (1/2” UNC capsule), 50 mV/Pa sensitivity
Data Storage for measurement data and audio (GB)   4 8
Remote Control from PC via USB (either through Serial Commands or Cloning of the Display)   Yes
Data Output   To PC, files can be saved as .csv for data viewing in spreadsheets ; audio recordings also saved in .csv files
Battery   Rechargeable Internal Battery, 2500 mAh
Capability to Connect to External Power Supply For long duration continuous measurement Yes, instrument can connect via USB port to power banks or charger
Internal Real-time Clock and Calendar   Yes
Size/Weight   210 x 85 x 55 mm( excl. microphone); 530 g ( including microphone)
Temperature/ Relative Humidity    -10 to +55 ⁰C; 0-95%
Colors   Blue and black Grey and black Red and black
Supply will include   Microphone (Class1 for SM90 / Class2 for SM50 AND SM30), USB charger, Intl. Charger adapters, measuring instrument, cables, windscreen, manual, carrying cord, USB flash drive with test signals & software tools in a ruggedized waterproof carrying case

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