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8
High-frequency Head and Torso Simulator (HF HATS) Type 5128 – User Manual
•
By using post-processing of the excitation signal provided to the mouth simulator. Caution
should be taken to ensure that the required sound pressure level is actually produced. See,
for example, ITU-T Rec.P.581
•
By using 'live' compression, that is, using a feedback signal from the mouth simulator output
to control the drive level to the mouth simulator. (This is easiest when a constant sound
pressure level is required. To obtain a predefined varying sound pressure level, a frequency-
dependent feedback network must be used.)
2.4
Ear Simulators
On delivery, HATS is fitted with a right and a left ear simulator. The ear simulator has a soft pinna
with a hardness very close to that of a real human pinna, furthermore it has a realistic ear canal.
This enables easy and realistic mounting of various types of headphones.
Most applications require that information about the actual sensitivity of the ear simulator is
provided. This can be accommodated in two ways:
•
By using transducer electronic data sheet (TEDS) information about the coupler, sensitivity
can automatically be transferred to the application software where it will be used when
performing measurements. When TEDS transducers are used, the need for performing a
calibration of the coupler can be omitted, since the risk of introducing errors during the
transfer of sensitivity information is extremely low.
•
By entering information about the coupler sensitivity from the data disk provided with HATS
to the application software that will be used for performing the measurements. In this case
the calibration procedure outlined below should be applied. Beside the coupler sensitivity
the data disk also holds other relevant data, for example, diffuse-field and free-field
corrections, see section 2.5.3 for more information
Fig.2.5.
Anatomical
Cross-section of the
head of HATS with the
ear simulator and
preamplifier fitted
Occluded Ear
Pinna (R)
Simulator (R)
Ear canal
Cable
guide
170209
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