#
AUDIO UNIT CONSTRUCTION/OPERATION

BHE092066900T03

• The audio unit is composed of the base unit, upper module, and lower module.

1 | Base unit
2 | Upper module (CD player or CD changer)
3 | Lower module (cassette deck or MD player)
4 | Cover (without upper module)

• Upper and lower module availability depends on vehicle grade.

## Terminal Layout and Signal

• (See CENTER PANEL MODULE CONSTRUCTION.)

## Base Unit

• The base unit controls the AM/FM tuner and upper/lower modules.

1 | Base unit

• An auto level control (ALC) function that controls speaker volume according to vehicle speed has been adopted.

## Auto Level Control (ALC) Function (Standard Specification Vehicle)

### Function

  • Adjusts the audio volume so that the sound is balanced against wind and road noise while driving.

### Operation

  • The audio unit changes the volume automatically based on the vehicle speed signal sent from the DSC HU/CM.

1 | Higher vehicle speed
2 | Lower vehicle speed
3 | Audio unit (base unit)
4 | Vehicle speed signal
5 | ALC circuit
6 | Power amplifier
7 | Speaker
8 | Higher volume
9 | Normal volume

  • The ALC function is divided into four modes, and can be used effectively to match the driving conditions.

Mode | Condition
--- | ---
| ALC function cancel
| Outside road noise low
| Outside road noise rather high
| Outside road noise high

## AudioPilot Function (BOSE specification vehicle)

### Function

  • Measures the driving noise level inside the vehicle with a specialized microphone, and the main amplifier modifies the volume accordingly. Due to this, passengers can enjoy music with constant sufficient volume.

### Construction/Operation

  • A microphone is installed on the lower panel.
  • The main amplifier separates the sound inside the vehicle, measured with a microphone, into music and noise, and compares the noise and music levels at each frequency. Then, volume compensation is performed for frequency bands where the noise is determined to interfere with the music.

1 | Main amplifier
2 | Noise
3 | Music
4 | Microphone
5 | Analysis
6 | Compensation
7 | Output to speakers
8 | Volume
9 | Compensated volume
10 | Music (set volume)
11 | Noise interference area
12 | Time
13 | Frequency band requiring compensation
14 | Low frequency
15 | High frequency
16 | Frequency
17 | SEC. A-A (compensation at each frequency)