JF Ptak Science Books Post 2377
Overall, these soldiers look to be in pretty good spirits, even if they were perhaps told to be so, they still looked fairly genuine. And who wouldn't be, at least to some degree, being survivors? They were a few of the millions of soldiers who were wounded in WWI, which means at least that they were among the millions of the dead.
The caption that accompanies these News Photo Service image (made by the Central News Photo Service and dated May 11, 1917, says that they were enjoying the donated headsets--Electrophones--and represented a few of the hundreds that received them. This device was basically a telephone receiver, and years after Bell and Edison dreamed of social integration and advancement and wide-ranging culture, of delivery literature and music to people flung near and far, these soldiers were enjoying the benefit of limited concerts and other entertainments via telephone lines.
[This lovely photograph is available at the blog's bookstore, here.]
Here's a very good quote ont he electrophone from the highly interesting The Cat's Meat Shop, written by Lee Jackson, author of Dirty Old London, the Victorian Campaign Against Filth. (It is an interesting topic--filth and its control--because you really can't have an Industrial Revolution without lots of workers living close to their jobs, which means that lots of people live close together, and you can't have that unless you somehow control for good sanitary conditions, which means you've got to take care of filth.)