Noise reduction device

A noise reduction device comprising:

• a noise controller configured to produce a control sound signal for canceling out noise;
• a control sound output component configured to output a control sound based on the control sound signal produced by the noise controller;
• a residual sound detector configured to detect a residual sound produced by superposition of noise and the control sound outputted from the control sound output component,
• a shell which envelops at least part of a seat configured to support a user in a substantially lying posture, at least a pair of the control sound output components and at least a pair of the residual sound detectors are installed in the shell,
• wherein the pair of the control sound output components are disposed substantially uniformly in the width direction with a center line in the width direction of the seat as a reference,
• the pair of the residual sound detectors are disposed substantially uniformly in the width direction with the center line as a reference;
• and wherein
• a difference between a first distance and a second distance satisfies the formula ΔL3=V/(6×f), the first distance corresponding to a distance from the control sound output component to the residual sound detector, the second distance corresponding to a distance from the control sound output component to a position of the user's ear,
• where ΔL3 is the difference between the first distance and the second distance, V (m/sec) is a speed of sound in air, and f (Hz) is a limit frequency at which a noise reduction effect can be obtained.