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What is the difference between Class 1 and Class 2?
The difference lies in the accuracy. Class1 are accurate to 0.1dB whereas Class2 are accurate to 0.5dB.
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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:
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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:
The Full STI module implements a novel measurement algorithm, that leverages the advanced signal processing capabilities of the SM50.
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:
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:
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.
| Function | Guideline / Application | SM50 | ||
| Modules / Functions | ||||
| Sound Pressure Level Meter (SPL / SLM) IEC-61672-1 : 2014, ANSI S1.4, | Class 2 / Type 2 | |||
| 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 |
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| 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 |
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| 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 | ||
| Acoustics | ||||
| 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 | Yes | ||
| Advanced Intelligibility Measurements (STIPA Pro) | For Public address systems, measure in 25 secs | Yes, with capability to enable/disable additive noise | ||
| Full STI (IEC-60268-16) | Most reliable complete STI measurement in 65 secs | Yes, 14 Modulation frequencies tested in 7 Octaves | ||
| Speech Level Meter | Yes, (CF. 602168-16) | |||
| Qualification Band Shown | A (Excellent) to U(Bad) | |||
| Acoustic Specifications | ||||
| Linear Range, Electric Input (dBuV) | 21 ~132dB | |||
| Measurement Range (dB) , Linear Range with Supplied Microphone, dBA SPL | 30 ~122dB | |||
| Frequency Range (Hz) | Covers entire range heard by human ear | 20 ~20.000 | ||
| Accuracy (dB) | 0.5 | |||
| 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 | |||
| Input | ||||
| Add Text Annotations to Measurements | Yes | |||
| Capability to Record Audio of all Measurements | Yes, in .wav format | |||
| Calibration | ||||
| 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 | |||
| Physical | ||||
| 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 | |||
| Data Storage for measurement data and audio (GB) | 4 | |||
| 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 â°C; 0-95% | |||
| Colors | Grey 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 | |||
The difference lies in the accuracy. Class1 are accurate to 0.1dB whereas Class2 are accurate to 0.5dB.
STIPA denotes speech intelligbility, i.e measurement of intelligibility of sound as heard by the user. The SM50 incorporates a scale which provides a measurement from A to E, classified as Excellent to Bad.
FullSTI takes about 1 minute to test , STIPA (more aimed at public address system takes 20 sec). Quick STIPA has an 18s test time.
Yes, it can perform Reverberation Time Meter (RT60), electro Acoustics (built in oscilloscope) & Sound Insulation-frequency dependent airborne sound insulation between rooms according to ISO- 16283-1:2014 (Dn, DnT and R') and ASTM E336.
A variety of statistical applications are built in the instrument , user selectable, such as LAEQ module for long term monitoring and logging , FFT, L Level for statistical distribution of sound levels during the measurement period.
SM50 is a class 2 meter. for Class 1, refer SM90.
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