User Guide

PAMS Technical Documentation System Module & UI

NHM-8NX

Issue 1 05/02 ãNokia Corporation Page 33

Figure 8: Speaker Interface

Earpiece Acoustic Design

The earpiece acoustics is designed to be type approved by type 3.2, low leak artificial ear

(Ear Simulator Type 4195, Low Leakage).

Three different types of A-covers is used for NHM-8NX: Standard cover, gaming cover

and DC-out cover. The gaming and DC-out covers is accessory covers. The std. A-cover

and the gaming cover comply with the same TA rules since they cannot be identified

HW- and SW-wise; this means that they match acoustical wise. However, the DC-out

cover can be identified, meaning that this type of cover is equalised separately.

In the assembly process the earpiece is placed into the lightguide from the front of the

phone. On top of this the metal frame is mounted.

The lightguide have stoppers in the bottom which lift the earpiece 0.3mm from the PWB

to provide leakage to the back.

On top of the lightguide is a metal frame which is the only visible part (in the earpiece

area) when the A-cover is removed. The metal frame covers the front of the earpiece to

provide protection against damage from fingers etc. The metal frame contain two acous-

tical holes in the area over the earpiece. These are placed as close to the vertical centre

of the phone as the design allows, in order to secure a sufficient sound pressure.

The metal frame have double-sided sealing in the earpiece area 1) downwards in order to

provide sealing and pressure against the top of the earpiece 2) upwards to provide seal-

ing to the A-cover. There is an opening in this gasket in the area on top of the metal

frame to provide better leakage to the internal volume.

The A-cover have a total of 5 acoustical holes positioned on a straight vertical line

through the centre of the phone. All holes are equal in size, elliptical in shape (each hole

approximates the area of a Ø1.3 hole). The three holes in top of the A-cover are posi-

tioned close to the metal frame hole in order to control loudness.

The A-cover includes a ring underneath which seals against the metal frame gasket. The

ring has a well defined opening of 5 mm (width). The opening has one main purpose: to

allow a dust shield to be mounted. Secondly the opening will provide better conditions

for obtaining good leak tolerant performance, than if only one A-cover hole was present.

All covers are optimised for the use of a dust shield, the specific type is Saatitech

PEC120/41.

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