Engine Intake Systems — Purpose of the Resonator In modern spark-ignition engines, what is the primary function of the intake resonator installed in the air-intake ducting?

Introduction / Context:
An intake resonator is a common plastic chamber connected to the air cleaner or intake ducting on passenger cars. Students often confuse it with performance devices like tuned runners. This question tests understanding of what the resonator mainly does in a production vehicle’s intake system.

Given Data / Assumptions:

• Road car with a conventional air filter box and ducting.
• No active valves or variable-geometry runners are part of the resonator itself.
• Goal is to identify the principal role under normal driving conditions.

Concept / Approach:
Air rushing past throttle plates and intake valves creates pressure pulsations. These pressure waves radiate as sound through the intake tract. A resonator is a side branch cavity (often Helmholtz-type) tuned to the dominant noise frequencies. By destructive interference, it attenuates objectionable intake roar, boom, and whistle without adding much restriction to airflow.

Step-by-Step Solution:
Recognize that a resonator is a passive acoustic device, not a flow controller.Its geometry (cavity volume and neck size) is chosen to target specific frequency bands produced by the engine.Therefore the best description of its job is to reduce intake air noise for NVH improvement.

Verification / Alternative check:
Vehicle NVH development routinely swaps resonator volumes and necks during testing to meet interior noise targets while maintaining pressure drop within limits. That confirms the acoustic, not metering, role.

Why Other Options Are Wrong:
Regulates intake flow rate: flow is set by throttle and engine demand, not the resonator.Enhances intake efficiency: any volumetric-efficiency gains are incidental; tuning runners do that, not the resonator.Regulates intake air temperature: that is a job for air path routing or active shutters, not the resonator.Dust separation: the air filter handles particulates.

Common Pitfalls:
Assuming “resonator” implies power increase; in production cars it is primarily an NVH component.

Final Answer:
reduces the intake air noise