The speaker on my smartphone is underwhelming; as is yours. I find myself cupping my hand around the base of the phone to provides a slight volume boost in situations with ambient noise. I wondered if it was possible to accomplish a volume boost with a spoon head acting as an amplification dish. The remainder of the spoon is bent into shape to act as a stand for the phone. The overall effect is a slight gain in volume (≈ 5dB in the video below); this is not an actual amplification but a deflection (and the spoon does not actually conform to a hyperbolic shape). No additional energy is needed to provide the sound boost, therefore it can be considered as "passive". There are several similar instructables out there, from the hand-cupping technique https://www.instructables.com/id/How-to-amplify-your-iPhone-speakerswith-your-ha/, some snazzy paper based variants https://www.instructables.com/id/iPad2-Speaker-Buddy/?ALLSTEPS and https://www.instructables.com/id/Make-any-iPhone-LOUDER-for-FREE-Megaphone-for-any/ and even some very elegant looking rigs https://www.instructables.com/id/Passive-amplifier-for-iPhone/.

Step 1: Step 2: Item List

All you need for this instructable is a spoon and some tools to bend it with. I started with a large soup spoon, thinking that I would want the larger surface area and length. The results was not great, due in part to the weight of the head, making the whole rig rather unstable. The best result was obtained from a cheap dessert spoon. This was easier to deform and not as top-heavy.

"Locking sheet metal tools" provide more control. Otherwise use what you have at hand. If you live in the Matrix, then use your mind.

TOOLS.tif
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Step 2: Step 3: Bend Spoon

This step covers the approach I took to bending the spoon(s). Depending on the size and quality of your cutlery, you may have to alter the length and angles to obtain the desired results. I used the "locking sheet metal tools" to do all the bending; this afforded more control on the position and angle of the bends. It is best to "underbend" rather than "overbend": the reason being that you will cause extra stress and eventually cause the spoon to break at the bend if you go back and forth. You can see a partial break on third image.

The glass of the iPhone in contact with the steel of the spoon has very little friction. You may elect to wrap some electrical tape along contact points to ensure secure positioning.

Step 3: Step 3: Enjoy

The uses for the "Spoon Amplifier" are limited to times when your best available screen is your phone (otherwise use your tv or computer), multiple people are watching (otherwise use your headphones), and you don't have access to external speakers (you're not home). Hunkering down to watch a movie with fellow hikers during a rain storm would meet these criteria.

If using a bent spoon is not sufficiently eco-geek-chic to impress your entourage, you can always build yourself a "passive" hearing aid like the one shown above. http://www.audioasylum.com/forums/hug/messages/14/146149.html