The Sony MDR-NC40 are over-the-head style headphones designed specifically for noise cancellation. The headphones feature 30 mm driver units combined with Neodymium magnets to reproduce strong bass and clear treble sound. They are capable of blocking up to 80% of external noise with a range of active noise attenuation of more than 14dB at 300Hz. The MDR-NC40 are designed with a lightweight, foldable headband, come with a travelling case for easy storage and portability, and have pressure-relieving ear cushions for additional comfort. The 5 ft cord has a built-in battery box with an on/off switch for controlling the noise cancelling feature. The battery life of the unit is approximately 40 hours and although a battery is required when using noise cancellation the headphones can still be used without a battery. The headphones are less advanced than Sony's MDR-NC60 headphones since they block a lower percentage of external noise and lack the built-in mointor switch, swivelling earcups, and single-sided detachable cord that come with the MDR-NC60s.
