1、 ANSI/CTA Standard Personal Sound Amplification Performance Criteria ANSI/CTA-2051 January 2017 NOTICE Consumer Technology Association (CTA) Standards, Bulletins and other technical publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and
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8、Requests to reproduce text, data, charts, figures or other material should be made to the Consumer Technology Association (CTA). (Formulated under the cognizance of the CTA R6 Portable, Handheld and In-Vehicle Electronics Committee.) Published by CONSUMER TECHNOLOGY ASSOCIATION 2017 Technology in pa
9、rticular there is no change in gain with change in input level. Limiting Signal processing to keep the output level from exceeding a threshold (i.e., limit), typically achieved by quickly reducing the gain applied to high-level input signals. Manikin (head and torso simulator) A head and torso simul
10、ator extending downward from the top of the head to the waist and designed to simulate the sound pick-up characteristics and acoustic diffraction produced by a median adult human head and torso. Multiband Equalization Frequency shaping achieved by separate adjustment of the gain in more than one ban
11、d. The resulting frequency response may be independent of level (simple equalization) or may change with level (level dependent frequency response). The latter is typically used for those desiring increased gain for soft high frequency sounds but do not wish loud low frequency sounds to be amplified
12、. Multiband Signal Processing The frequency bandwidth of the device is divided into more than one band, enabling individual control of the processing in each band. Example use cases are compression, equalization, noise rejection, and feedback rejection. 4 CTA-2051 Occluded Ear Simulator A device use
13、d for testing which approximates the acoustic transfer impedance of the inner part of the human ear canal, from the tip acoustic output of an ear mold insert device to the eardrum. In the case of hearing devices that do not insert into the ear canal, e.g. earphones that are designed to lay in the co
14、ncha or be laced over the ear, a Head and Torso Simulator, as defined in ANSI S3.36 is appropriate for testing. Real Ear Coupler Difference Denotes the difference between (a) the response of an in-situ device measured at the eardrum and (b) the same device measured in a coupler. Average values of th
15、ese differences are shown in Table 4.1C. Single Band Signal Processing Signal processing (e.g., compression) applied by treating the entire frequency bandwidth of the device as a single channel. THD+N Denotes Total Harmonic Distortion plus Noise. It represents (a) the sum of the powers of all harmon
16、ic distortion components plus noise divided by (b) the power of the fundamental (test) signal frequency. The square root of this ratio is expressed in percent. Wide Dynamic Range Compression Non-linear processing that is differentially applied to sounds as a function of their level. It is typically
17、done so as to amplify soft sounds more so than loud sounds, thereby reducing the dynamic range. NOTE: Wide Dynamic Range Compression and Limiting are similar in process but different in degree and perceived effect. 3.1 Symbols and Abbreviations AGC Automatic Gain Control CORFIG Coupler Response for
18、Flat Insertion Gain dB Decibel dBA A-weighted Decibels OSPL Output Sound Pressure Level RECD Real Ear Coupler Difference SNR Signal to Noise Ratio SPL Sound Pressure Level THD Total Harmonic Distortion 4 Criteria for Standardization Three categories of standardization level are defined and described
19、 below. These categories identify three levels of technical performance specification differentiated by a decrease in the degree of standardized specification required for fulfilment of the feature requirements. The level of performance specification recommended by this document for each feature is
20、independently identified for each feature within the associated sub-section. Measurement methods for evaluation of all relevant metrics characterized in the feature specific sub-sections are identified and described when appropriate. Category 1: The description of a hearing device performance parame
21、ter which must include the value measured per the specified testing method. Category 1 requirements include a threshold or acceptable 5 CTA-2051 range for the parameter measured. Category 2: The description of a hearing device performance parameter which must include the value measured per the speci
22、fied testing method. Category 2 requirements do not include a threshold or acceptable range for the parameter measured. Category 3: Presence of the technological capability or feature shall be reported in the device description. The specific value/metric for measurement of this value is not within t
23、he scope of the standard. Measurements in this standard specify the use of tones (sine waves) as a stimulus signal. It is recognized that many devices will include non-linear audio processing (DSP) (for example, noise suppression, band equalization) that may cause unexpected test results when tones
24、are used as test stimulus signals. Therefore, when performing measurements using tones as specified in Section 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, and 4.7, any non-linear signal processing should be disabled. Alternatively, if using tones is not appropriate for testing a specific device, for example, due
25、to the inability to disable non-linear processing, alternative test signals such as real speech and 1/3rdoctave pulsed noise signals may be used. If an alternate test signal is used, 1/3rdoctave analysis should be performed to obtain individual frequency based test results, similar to what would hav
26、e been obtained if tone-based measurements were performed. As in ANSI S3.22-2014, Section 5.2.5, controls of the device under test shall be set for the widest available frequency response range, e.g., tone control typically set for minimum effect. As in ANSI S3.22-2014, Section 4.1, test signal(s) s
27、hall exceed background noise by at least 10 dB, and unwanted stimuli shall be sufficiently low so as not to affect the test results by more than 1 dB. In addition to the tests included in this standard, it is recommended that informal listening tests be performed during both product development and
28、final evaluation to ensure that there are no undesirable effects present that are not revealed by objective testing. Category 1 4.1 Frequency Response Bandwidth (Category 1) Frequency Response Bandwidth of a sound reproduction system relates to the portion of the input acoustic spectrum that the dev
29、ice can provide to a user. A consistent methodology for measurement (relative to a common reference) and assessment of the spectrum width provides the consumer a means to compare and evaluate competing systems. The upper and lower cut off frequencies are defined as the frequencies at which the estim
30、ated insertion response falls 10 dB relative to the average level of the insertion gain in the one-third octave bands from 500 to 3150 Hz. The low frequency cut off for all devices shall extend to 250 Hz or below. Devices labeled as “Standard Band” shall have an upper cut off frequency of 5 kHz or g
31、reater. Devices labeled as Wide Band shall have an upper cut off frequency of 10 kHz or greater. Frequency response bandwidth shall be reported and labeled on the packaging. Method: Frequency response is measured in a coupler according to ANSI S3.22-2014 using an 80 dB SPL input signal. The one-thir
32、d-octave insertion gain response shall be calculated from the values of the pressure response measured in a 2cc coupler or an occluded ear-simulator coupler (as specified in IEC 60318-4, commonly called a “711“ coupler). 6 CTA-2051 To obtain the one-third-octave insertion response, the appropriate C
33、ORFIG corrections needed to obtain insertion gain are used in each case. These CORFIG corrections are shown in Tables 4.1A and 4.1B for the 2cc coupler and the occluded ear-simulator coupler, respectively. When bandwidths above 8 kHz are to be verified the occluded ear simulator coupler must be used
34、. The components underlying the overall CORFIGs are given in Table 4.1C. For example, it shows that the choice of microphone location generally results in a small correction. The corrections provided are applicable for hearing devices with microphone positions that are typical for in the ear (ITE) a
35、nd behind the ear (BTE) device configurations. If a hearing device with a microphone position other than described above is to be tested, then an appropriate correction to a diffuse field simulation may be needed to account for the devices microphone position in addition to the corrections for the e
36、ar simulator coupling. Table 4.1A: CORFIG corrections for converting 2cc coupler response to estimated insertion gain assuming diffuse-field measurement. Values are given for device microphone locations that are in the ear (ITE) and behind the ear (BTE) at one-third octave center frequencies (Freq).
37、 Freq ITE CORFIG (2cc) BTE CORFIG (2cc) Hz dB dB 125 -3.5 -3.5 160 -3.5 -3.5 200 -3.3 -3.3 250 -3.4 -3.3 315 -3.5 -3.3 400 -3.5 -3.1 500 -3.3 -3.0 630 -3.1 -3.0 800 -2.8 -2.7 1000 -2.9 -2.7 1250 -2.4 -2.5 1600 -1.1 -1.3 2000 1.3 1.2 2500 3.4 3.9 3150 0.9 1.9 4000 -4.1 -2.1 5000 -7.9 -6.1 6300 -11.0
38、-10.1 8000 -14.5 -13.2 7 CTA-2051 Table 4.1B: CORFIG corrections for converting Occluded Ear Simulator response to estimated insertion gain including corrections to simulate a diffuse-field measurement. Freq ITE CORFIG (Ear Simulator) BTE CORFIG (Ear Simulator) Hz dB dB 125 0 0 160 0 0 200 0.2 0.2 2
39、50 0.1 0.2 315 0 0.2 400 0 0.4 500 0.3 0.6 630 0.9 1.0 800 1.7 1.8 1000 2.1 2.3 1250 3.3 3.2 1600 5.2 5.0 2000 8.4 8.3 2500 11.9 12.4 3150 10.9 11.9 4000 7.4 9.4 5000 5.5 7.3 6300 4.2 5.1 8000 2.5 3.8 10000 1.1 2.3 12500 -1.2 0.1 16000 -1.5 -1.0 8 CTA-2051 Table 4.1C: Details underlying the set of C
40、ORFIG diffuse field corrections used in Tables 4.1A and 4.1B. CORFIG formulae based on microphone location (A1 and A2), acoustic coupler (B1 and B2), and the diffuse field response of the open ear, measured at the eardrum (C). The combination of these data generate four CORFIG responses, (D1, D2, E1
41、 and E2): D1 is the ITE, 2cc coupler CORFIG: D1 = C - B1 A1; D2 is the BTE, 2cc coupler CORFIG: D2 = C B1 A2; E1 is the ITE, Occluded Ear Simulator CORFIG: E1 = C B2 A1; E2 is the BTE, Occluded Ear Simulator CORFIG: E2 = C B2 A2. A1 A2 B1 B2 C D1 D2 E1 E2 One third octave centers SPL increase at Mic
42、rophone location re: diffuse field SPL SPL increase at Microphone location re: diffuse field SPL SPL increase at eardrum re: 2cc coupler SPL increase at eardrum re: ear simulator SPL increase at eardrum re: diffuse field SPL 2cc Coupler CORFIG Occluded Ear Simulator CORFIG Freq Microphone location c
43、orrection Real Ear to Coupler Difference (RECD) Diffuse Field Response of the Open Ear ITE MIC BTE MIC 2cc Occluded Ear Simulator ITE CORFIG BTE CORFIG ITE CORFIG BTE CORFIG Hz dB dB dB dB dB dB dB dB dB 125 0.2 0.2 3.5 0 0.2 -3.5 -3.5 0 0 160 0.3 0.3 3.5 0 0.3 -3.5 -3.5 0 0 200 0.3 0.3 3.5 0 0.5 -3
44、.3 -3.3 0.2 0.2 250 0.5 0.4 3.5 0 0.6 -3.4 -3.3 0.1 0.2 315 0.8 0.6 3.5 0 0.8 -3.5 -3.3 0 0.2 400 1.2 0.8 3.5 0 1.2 -3.5 -3.1 0 0.4 500 1.3 1.0 3.6 0 1.6 -3.3 -3.0 0.3 0.6 630 1.3 1.2 4.0 0 2.2 -3.1 -3.0 0.9 1.0 800 1.3 1.2 4.5 0 3.0 -2.8 -2.7 1.7 1.8 1000 1.8 1.6 5.0 0 3.9 -2.9 -2.7 2.1 2.3 1250 2.
45、1 2.2 5.7 0 5.4 -2.4 -2.5 3.3 3.2 1600 2.4 2.6 6.3 0 7.6 -1.1 -1.3 5.2 5.0 2000 2.7 2.8 7.1 0 11.1 1.3 1.2 8.4 8.3 2500 3.3 2.8 8.5 0 15.2 3.4 3.9 11.9 12.4 3150 4.0 3.0 10.0 0 14.9 0.9 1.9 10.9 11.9 4000 5.2 3.2 11.5 0 12.6 -4.1 -2.1 7.4 9.4 5000 5.4 3.6 13.4 0 10.9 -7.9 -6.1 5.5 7.3 6300 5.0 4.1 1
46、5.2 0 9.2 -11.0 -10.1 4.2 5.1 8000 6.0 4.7 17.0 0 8.5 -14.5 -13.2 2.5 3.8 10000 5.8 4.6 0 6.9 1.1 2.3 12500 5.7 4.4 0 4.5 -1.2 0.1 16000 4.5 4.0 0 3.0 -1.5 -1.0 9 CTA-2051 4.2 Frequency Response Smoothness (Category 1) Frequency Response Smoothness of a sound reproduction system relates to user expe
47、rience of fidelity or consistent performance across frequency. A limit on maximum deviation is specified to ensure that sufficient smoothness is achieved. No single peak in the one-third-octave frequency response shall exceed 12 dB relative to the average levels of the one-third-octave bands two-thi
48、rds octave above and below the peak. Example: A peak at 1.6 kHz should be compared to the average of the 1.0 kHz and 2.5 kHz one-third-octave levels. The frequency response evaluated for this parameter shall be the diffuse field corrected one-third-octave frequency insertion response as specified in
49、 4.1. 4.3 Maximum Acoustic Output (Category 1) Maximum Acoustic Output relates to user comfort, in particular to avoid uncomfortably loud sounds. A criterion for maximum output provides a minimum performance standard for user comfort. The maximum OSPL90 output level shall not exceed 120 dB SPL measured in a 2cc coupler. Refer to ANSI S3.22-2014 for OSPL90 measurement conditions. Note: A 120 dB SPL measured in a 2cc coupler is equivalent to a level of approximately 115 dBA referred to the sound field. See Annex A for more information. 4.4 Distortion Control Limi
