My client reports the Zen Noise to be intermittent/pulsating
The risk with Zen noise is that the compressors in the hearing aid can affect Zen noise as it is a soft input at the same time as the compressors are trying to use microphone squelch (expansion) to reduce circuit noise levels.  This can result in reports of Zen noise pulsing or Zen noise being intermittent.  The Zen tones do not have this issue due to the natural pauses between the music.