More and more sounds can only be heard in our memories. So many have disappeared within my lifetime so far:
1. All-metal rollerskates on the sidewalk. Nylon wheels just don't have the same ratchety sound.
2. The rumble of car tires on brick streets.
3. Actual ringers in phones, including when you bang the receiver down, the bell inside responds with a clong!
4. A percolator, on the stove or plugged in, slowing down through those last majestic upheavals (is it done? No, one more long snort...)
5. Two-noted police whistles urging either people (two notes) or cars (one note) to get themselves moving. The traffic cops don't even seem to own whistles anymore. (This may be specific to Chicago.)
6. The promising hissssss heard after dropping the phonograph needle on a record, before the music starts. I'm having some old favorite albums put on CD and I've asked the guy to leave the hiss on at the beginning; it doesn't sound right otherwise.
7. The row of real chiming bells on the ice cream trucks (endless amplified "Oh Susanna" will greet all who enter Gehenna) AND (to date myself) the two-noted cowbell sound of the scissor-and-knife-sharpening cart that used to come down the alleys.
There must be more. Your memories, please?
Yikes: will today's ten-year-olds sigh over the sound of a bug zapper? Twenty-year-olds get teary-eyed over the sound of a hard drive booting up? Thirty-year-olds smile at the sound of Pong?