Noise in electrostatic recording

Playback noise in electrostatic recording is due to random electrical charge patterns on and in the dielectric tape record. Surface charges on the tape may be neutralized by passing the tape through an ion bath, which greatly reduces the playback noise level, particularly at low frequencies. The noise of such neutralized tapes may be interpreted in terms of a random array of charged regions in the tape having an average diameter of 0.04 cm and a charge density of 5 esu/cm². Charge injection during recording changes this charge pattern but results in a similar array of smaller charged spots, 3 × 10^-5cm in diameter. This recorded noise is due to the spark-like character of the recording discharge and may be reduced by generating a continuous discharge.