CALIBRATION OF SOUND METERS AND ACOUSTIC CALIBRATORS
“Regular calibrations guarantee high-quality and traceable data, minimizing the risk of measurement errors and associated costs”
The acoustic laboratory of K2 Ingeniería is accredited by the ONAC under ISO 17025 to perform periodic calibrations of sound level meters and acoustic calibrators. The laboratory has state-of-the-art equipment that allows the calibration of class 1 or class 2 integrating sound level meters, according to the procedures described in IEC 61672-3.
Calibration procedures help you meet national and international requirements for:
The K2 Engineering laboratory can perform the metrological calibration of sound level meters, for the issuance of certifications related to the control of acoustic measuring instruments in service.
The various regulatory and technical tests are intended to verify and confirm that an instrument in service maintains, since its last verification, the metrological characteristics that correspond to it according to the approval of its model and to verify that it works according to its design and its specific regulations. To evaluate the conformity of these acoustic instruments, the deviations of the model are examined according to the maximum errors established by the International Electrotechnical Commission and its electroacoustic standard IEC 61672-1.
Periodic sound level meter calibration tests include:
- Preliminary inspection.
- Verification of the power supply.
- Indication of the calibration check frequency.
- Intrinsic noise with microphone installed.
- Intrinsic noise with the microphone replaced by the electrical signal input device.
- A frequency weighting with acoustic signals.
- Frequency weightings with electrical signals.
- Frequency and time weightings at 1 kHz.
- Long-term stability.
- Level linearity in the range of reference levels.
- Response to wave trains.
- Peak C-weighted sound level.
The following technical measurement tests are carried out in the laboratory, in accordance with the quality requirements of the IEC standards.
Sound level meter calibration
- Indication of the calibration check frequency: The sensitivity of the microphone is verified by exposing it to a constant sound pressure level produced by an acoustic calibrator or pistonphone. The necessary adjustment is applied to compensate for the deviation in sensitivity.
- A frequency weighting with acoustic signals: The frequency weighting network A is verified at the frequencies of 125 Hz, 1 kHz and 8 kHz using an electrostatic actuator to simulate an acoustic pressure on the microphone membrane.
- Frequency weightings with electrical signals: The frequency weighting networks A, C and Z (Lin) are verified at frequencies of 1/3 octave from 63 Hz to 16 kHz, replacing the microphone with an adapter device which inputs electrical signals to the sound level meter. Subsequently, the necessary corrections are applied to obtain the acoustic level that would be obtained in free field and the levels relative to the level indicated at 1 kHz are calculated.
- Frequency and time weightings at 1 kHz: The frequency weighting networks A, C, Z, the Fast and Slow time weighting networks and the equivalent continuous level are verified in response to an electrical signal produced by the reference level at 1 kHz.
- Long-term stability: Indicated levels are compared in response to an electrical signal that produces the Reference Level at 1 kHz; at the beginning and end of a period of 25 to 30 minutes of continuous operation of the sound level meter. Then the difference between the two indications is verified.
- Linearity level in the range of reference levels: deviations are checked results using electrical signals 8 kHz 5 dB intervals covering the entire measurement range the meter, compared to a linear behavior.
- Response to wave trains: The transient response of the sound level meter is verified using fragments of different durations extracted from continuous sinusoidal signals at 4 kHz in Fast and Slow weightings, and in the sound exposure level.
- Peak C level: The difference between the peak C level and the C weighted level is verified, using complete cycles, positive and negative half cycles at 8 kHz and 500 Hz of sinusoidal electrical signals.
- Overload indication: The difference between the level that indicates the overload signal in response to positive half cycles of a 4 kHz sinusoidal signal and the level that indicates the overload in response to negative half cycles is verified.
- Stability at high levels: The difference between the indication at the beginning and the end of a continuous 5-minute period is verified, during which the sound level meter is exposed to a level close to the overload indication using a sinusoidal electrical signal of 1 kHz.
In addition to the above tests, the following are performed:
- Intrinsic acoustic noise: The instrument’s own noise is verified with the microphone installed and under controlled acoustic external noise conditions.
- Intrinsic electrical noise: The instrument’s own noise is verified by replacing the microphone with an adapter that simulates the same capacitance of the microphone and grounding it to determine the electrical noise of the sound level meter.
- Power supply: It is verified that the power supply delivered with the meter has a voltage within the limits defined by the manufacturer of the meter.
- Sound pressure level: The pressure level of the calibrator or pistonphone is verified if it is 94 dB at 1 kHz. To determine this, a direct comparison is made against a reference standard with certified calibration.
- Frequency: The frequency of the acoustic signal emitted by the calibrator or pistonphone is verified. The result is given as a percentage error with respect to the nominal level.
- THD + N: The harmonic distortion plus noise of the acoustic signal emitted by the calibrator or pistonphone is verified. The result is given in percentage of distortion.
Calibration certificate: the calibration certificate is delivered according to the standards of the International Electrotechnical Commission (includes conformity results and their associated uncertainties).
Hardware preventive maintenance: General cleaning of the sound level meter by highly qualified professionals.