I suppose it would depend on the exact gyroscope; apparently some are more sensitive to audio frequency noise than others; some details in this document:

http://www.invensense.com/mems/gyro/documents/whitepapers/A%...

Its placement within the device will also affect the sensitivity to audio, so it will vary between device models - the article doesn't mention if 65% is worst-case, best-case, or an average.