BS EN 50332-1:2013 Sound system equipment: Headphones and earphones associated with personal music players – Maximum sound pressure level measurement methodology Part 1: General method for ” one package equipment “
BS EN 50332-1:2013 pdf free.Sound system equipment: Headphones and earphones associated with personal music players – Maximum sound pressure level measurement methodology Part 1: General method for ” one package equipment “.
4 Measuring principle
4.1 General description
The free field frequency response of a head and torso simulator is defined as follows:
The difference, as a function of frequency, between the sound pressure level at the ear simulator microphone with the reference point of the manikin at the test point and the sound pressure level at the test point with the manikin absent from a sound source at the 0 degree azimuth and 0 degree elevation angles.
The diffuse field frequency response of a head and torso simulator is defined as follows:
The difference, as a function of frequency, between the sound pressure level at the ear simulator microphone with the reference point of the manikin at the test point and the sound pressure level at the test point with the manikin absent from a sound field with a high number of reflections that, at any given point in that diffuse field, sound arrives from all angles in a uniform manner.
The sound pressure level produced by headphones or earphones can be measured by subjective methods or by objective methods.
The reference method for evaluating the sound pressure level emitted by earphones is a psycho acoustic method known as “equal loudness” (EN 60268-7). It consists in using human test subjects to compare the level of sound emitted by a speaker to that emitted by an earphone.
Nevertheless, this subjective method becomes inadequate — and hazardous — when high levels are to be evaluated.
The solution is to use an objective measurement method, giving both a good reproducibility and a good correlation with subjective tests.
4.2 Measuring principle
This standard is based on the use of a Head and Torso Simulator (HATS). The manikin in accordance with IEC 60318-7 is fitted with an occluded ear simulator (as described in EN 60318-4) and an ear canal extension (8.8 mm length and diameter 7.5 mm ± 0,02 mm). Alternatively, the HATS as described in ITU-T P.58 in conjunction with ITU-T P.57 may be used, which is usually used for telephonometric use.
NOTE I Industrial realisation of these sam.iators use pinnaes 01 different material properties leading to different results Thus, the type of pinnae needs to be stated in the measurement protocoL
NOTE 2 Because the full range of equipment covered by this standard used to be measured with two different types of HATS. this standard offers to select between both.
The sound pressure level measured by the ear simulator microphone represents the pressure found at eardrum level and differs from that of the free field or diffuse field pressure by the HATS transfer function.
Free field (0-0 free field) or diffuse field response shall be used.
Weighting curve A shall be used.
The results are given as “(free field) or (diffuse field) related A-weighted equivalent continuous sound pressure levels (LAeq).
5 Test signal
Actual musical signals are continuously fluctuating in both amplitude and spectral contents and thus cannot be used as test signals.
As the frequency response curve of earphones may show considerable fluctuations, accurate measurements cannot be performed using a sinusoidal signal at a determined frequency (e.g. 1 kHz).
The test signal shall therefore be a full audio frequency band for the equipment under test, the spectral content of which is representative of the musical signals.
The test signal used to determine the maximum sound pressure level of headphones shall be programme simulation noise, as defined in HD 483.1 S2.
NOTE 1 HD 483.1 S2 defines a test signal called “programme simulation signal” descnbed as: “A signal whose mean power spectral density closely resembles the average of the mean power spectral densities of a wide range of programme material, including boUi speech and music of several kinds”. This signal is a weighted stationary Gaussian noise and can be obtained from pink noise with a statable filter network.
This programme simulation noise shall have a crest factor ranging between 1,8 and 2,2. Thus, this signal will be easy to record on various media.
Since portable cassette and CD players are playback only devices, it is necessary to define a reference cassette and a reference CD for test.
The test signal level is a major issue, as the whole measuring process will depend on this setting.
5.2 Test signal level for analogue recorders
With analogue tape recording on compact cassette, -o dB level recording corresponds by definition to a flux value of 250 nWblm at a frequency of 315 Hz (EN 60094-2).
The recording level of the test cassette shall be set considenng both the frequency spectrum and the crest factor of programme simulation noise:
— the test recording tape shall be type 1 magnetic tape according to EN 60094-7;
— the test signal shall be recorded at an RMS value of- 6 dB (ref 250 nWb/m at 315 Hz):
— the noise reduction system shall be switched off.
5.3 Test signal level for FM radio
Measurements on receivers for frequency modulated sound broadcasting emissions are defined in
NOTE Signal peak to peak lev at a recevers output is direct’y proportional to the peak frequency deviation of the RF camer.
In order to comply with the definition of maximum peak frequency deviation (determined with a sinusoidal modulating waveform), and to take into account pre-emphasis influence, the test signal applied at the input of the RF generator shall be set at an RMS value of – 6 dB related to the amplitude of a sinusoidal waveform at 250 Hz, producing a peak to peak deviation of ± 75 kHz.
5.4 Test signal level for digital music players
This subclause also covers DAB players and music players as part of other digital equipment, such as mobile phones.
The test signal is the programme simulation noise as defined in HO 483.1 S2. For digital listening devices, the test signal shall be applied to the listening device with an r.m.s. amplitude of – 10 dBFS. where 0 dBFS is defined as being the maximum RMS amplitude of a sinusoidal signal corresponding to the full scale of the digital interface,
The test signal shall be recorded, prior to the test, into the memory of the personal music player or on any appropriate media in a lossless format (such as WAy). The recorded signal shall not be clipped.BS EN 50332-1 pdf download.BS EN 50332-1:2013 Sound system equipment: Headphones and earphones associated with personal music players – Maximum sound pressure level measurement methodology Part 1: General method for ” one package equipment “