idb and ivibe Performance Tests Sound

Transcription

1 idb and Performance Tests Sound Identical circuits are used in both instruments and in what follows we refer to them collectively as. The sound processing circuits are designed to meet the Class 1 requirements of BS EN :2013. The ultimate performance of the instrument will depend on whether a Class 1 or Class 2 microphone is used. The following tables and charts give details of the typical performance of the idb and instruments when an electrical stimulus is applied instead of the microphone. For the purpose of these tests, the instrument was calibrated to give a reading of 94.0 when a 50.0 mv RMS 1.0 khz sine wave stimulus is applied to the microphone input. The ACO 7146 Class 1 microphone (with integral preamplifier) normally supplied with the has a typical sensitivity of 42.2 mv/pa at 1.0 khz (i.e. about -1.4 less). A typical performance chart for this microphone is given in the Appendix The records inputs between +30 and +125 on a single range with a linearity of better the ±0.5 for inputs greater than 40. The noise floor, as measured with the microphone input shorted, is typically 25 or less for both the A and C weightings with 50mV/Pa sensitivity. is able to measure and record A and C frequency weightings simultaneously together with LCpeak and overload time as a percentage of measuring time. Both instruments also contain an accurate atmospheric pressure sensor. For the purposes of these tests, the stimulus signals were generated by a TTi 50 MHz Function Generator (Model TG5011) and the RMS stimulus voltages measured by a Keysight 6.5 digit DVM (Model 34461A). A precision attenuator was also used. The test results confirm that the performance of the idb and sound processing circuits exceed the Class 1 requirements of BS EN :2013. & idb sound processor performance 1

2 Frequency Weightings - BS EN Section mv RMS sine wave applied giving a reading of at 1.0 khz Frequency Hz BS Deviation Class 1 tolerance A C A C A C , - infinity , - infinity , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , - infinity & idb sound processor performance 2

3 50.0 mv RMS sine wave applied giving a reading of 94.0 at 1.0 khz Frequency Hz BS Deviation Class 1 tolerance A C A C A C < , - infinity , - infinity , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , - infinity & idb sound processor performance 3

4 158.1 µv RMS sine wave applied giving a reading of 64.0 at 1.0 khz Frequency Hz BS Deviation Class 1 tolerance A C A C A C < , - infinity < , - infinity < , < , < , < , < , < , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , - infinity Note: µv signal generated using a attenuator & idb sound processor performance 4

5 Deviation from Class 1 () Deviation from Class 1 () Deviation from Class 1 () A & C weighting at 500 mv RMS Frequency (Hz) Tolerance Tolerance A-weighting C-weighting A & C weighting at 50 mv RMS Frequency (Hz) Tolerance Tolerance A-weighting C-weighting A & C weighting at 158µV RMS Frequency (Hz) Tolerance Tolerance A-weighting C-weighting & idb sound processor performance 5

6 Level Linearity - BS EN Section 5.5 has a single measurement range spanning 95 for sound pressure levels between 30 and 125 for both A and C frequency weightings. Performance tests were carried out at frequencies of 4.0 khz, 1.0 khz and 40 Hz. Stimuli below 10 mv RMS were generated with the aid of a precision attenuator. For BS Class 1, the linearity deviations (Dev.) shall not exceed ±0.8 over the linear measurement range of the instrument and shall not exceed ±0.3 within any 10 portion thereof. Level Linearity at 4.0 khz Stimulus mv RMS True A A Dev. A True C C Dev. C Level Linearity at 1.0 khz Stimulus mv RMS True A A Dev. A True C C Dev. C & idb sound processor performance 6

7 Response Level Linearity at 40 Hz Stimulus mv RMS True A A Dev. A True C C Dev. C < < , < < A-weighted linearity, 4.0 khz A weighted response Stimulus Linear (A weighted response) y = x R² = & idb sound processor performance 7

8 Response Response C-weighted linearity, 4.0 khz C weighted response Stimulus Linear (C weighted response) y = x R² = A-weighted linearity, 1.0 khz A weighted response Stimulus Linear (A weighted response) y = x R² = & idb sound processor performance 8

9 Response () Response C-weighted linearity, 1.0 khz C-weighted response Stimulus Linear (C-weighted response) y = x R² = A-weighted linearity, 40Hz A-weighted response Stimulus () Linear (A-weighted response) y = x R² = & idb sound processor performance 9

10 Response () C-weighted linearity, 40 Hz C-weighted response Stimulus () Linear (C-weighted response) y = x R² = Noise Floor - BS EN Section 5.7 A -weighting C-weighting Maximum noise floor at 50mV/Pa Level at which noise floor causes a non-linearity of < 0.4 Level at which noise floor causes a non-linearity of < Time-weightings F and S BS EN Section 5.8 uses digital filters to meet the design goal time constants of sec for the F time weight filter and 1.0 sec for the S time weight filter. Their accuracy is confirmed by the accuracy of the following toneburst measurements. & idb sound processor performance 10

11 Toneburst response () Toneburst Response - BS EN Section khz toneburst, Lmax response, F time weighting : LA= 114.8, : Lc =113.0 Toneburst Duration ms BS L AFmax - L A L CFmax L C L AFmax - L A L CFmax L C L AFmax L CFmax Class 1 Tol. + Class 1 Tol Tonebust L max F Response Toneburst duration (ms) BS EN Class 1 A-weight C-weight & idb sound processor performance 11

12 Toneburst Response () 4.0 khz toneburst, Lmax response, S time weighting : LA= 114.8, : Lc =113.0 Toneburst Duration ms BS L ASmax - L A L CSmax L C L ASmax - L A L CSmax L C L ASmax L CSmax Class 1 Tol. + Class 1 Tol Tonebust L max S Response Toneburst Duration (ms) BS EN Class 1 A-weight C-weight & idb sound processor performance 12

13 Toneburst response () 4.0 khz toneburst, Leq response, F time weighting : LA= 114.8, : Lc =113.0 Toneburst Duration ms BS L AE - L A L CE L C L AE - L A L CE L C L AE L CE Class 1 Tol. + Class 1 Tol Toneburst L eq F Response Toneburst duration (ms) BS Class 1 A-weight C-weight & idb sound processor performance 13

14 C-weighted peak sound level - BS EN Section 5.13 Cycles Frequency Hz BS Tol. L Cpeak-L C L Cpeak-L C L Cpeak L C Class 1 one , -2 one , -1 one , -2 +half cycle , -1 -half cycle , -1 NOTES Revision history: Issue 1, 18 October 2016, original 2016, Turnkey, MJL, Issue1 Turnkey, and idb are registered trademarks & idb sound processor performance 14

15 APPENDIX CLASS 1 MICROPHONE PERFORMANCE & idb sound processor performance 15