I've been discussing this with my therapist today, we think selecting noise that promotes slow-wave sleep might help. I've been exploring the use of structured noise to do this e.g:

Frontiers | Acoustic Enhancement of Sleep Slow Oscillations and Concomitant Memory Improvement in Older Adults | Frontiers in Human Neuroscience

Also thinking of buying some of these:

SleepPhones v6 Wireless Bluetooth Portable Headband: Amazon.co.uk: Electronics