The environment within the cabin of a sleeper train is, well, unusual. Quite contradictory. It feels empty when you first step in, but full seconds later. It has a dead quiet feel, whilst also being noisy. It affords little physical space to move about in, yet anything you accidentally drop ends up out of reach. It would feel claustrophobic too if it weren't also strangely spatial when the lights are out. It has bareness and simplicity that somehow affords comfort. And the cabin often rocks about, as do you. The sound-feel within the cabin is unusual too. To start with there's rumble. Rumblings that roll constantly while the train is in motion. Sudden low frequency thuds and judders, as the carriages roll over joints and points in the track. There are regular pressure bumps in the internal air caused by trains passing close by in the opposite direction, and multiple strong humming sounds from the air conditioning and electric motors operating the train. Delicate sounds too. Tiny creaks and subtle shiftings in the fabrics and panelling that line the cabin, especially the ceiling which is made of flexible sound-absorbing slats.  To be conducive to sleep you'd have thought the cabin ideally needs none of this. Yet there is  an intense stillness. And during your considerable time in the cabin, twelve hours and more, these aural qualities interact, and form into their own rhythms. The mental chemistry of it all reacts to produce soporific calm. Set against my knees (as I slept) and the side wall of the cabin, with no inches to spare and bed clothes pushed up all around which would normally scupper any spatial recording, the Lento box recorded as the "night" began. Sleeping on a sleeper train is not like any normal night of course. The whole world around you is moving, rocking, as is everything in the soundscape. And yet you get your head into the comfortable hinged pillow (the back half goes up forming a bump protector) and you enter into a long aurally enhanced doze, that may, if you are lucky, become proper sleep.  Listening back the Lento box captured a true impression of being in a sleeper train cabin. Including occasional bed covers shifting and one of us popping out of the cabin briefly which is all part and parcel of the sound experience. This passage of time is somewhere between 3am and 4am. The train is speeding steadily across France, passing through lamplit towns and cities as it rolls on through the night. (It's hard to resist sleeping with the window blind part rolled up so you can witness these truly marvellous scenes.) The journey on this SNCF service is over 850km, departing Cerbere station on the extreme southern coast of France at 1850hrs, arriving Paris Gare d'Austerlitz at breakfast time the next morning.