The Sounds of Summer

Ah, the sounds of summer, a summer now almost free of Covid-19.

The sweet song of the ice cream truck, the cooing of doves, the reverberating bounce of a basketball, the shrieks of kids doing whatever kids do.

The night also has sounds, some good and some annoying.  One of the worst is the hum, buzz, click clacks, and muffled sobs of air-conditioning.  The just-as-you're-fallling asleep blare of the air conditioner cycling. 

 Turning the volume of your television so high that folks a mile away can hear it, so that you can hear it over the air conditioner.

Why are air conditioners noisy? What are all of those dissonant sounds? 

The basis of air-conditioning seems simple: a compressed gas released through a small hole becomes extremely cold.  The heat inside shifts eagerly to the cold air and is then whisked away. Something like that. 

As suggested, an air conditioner has a compressor.  It's there to compress a refrigerant, which means a chemical that destroys ozone, or it used to.  Safer refrigerants are now used.

Once the refrigerant is cold, it is circulated through a series of tubes, which unwound, would be a zillion miles long.  The circulating cold in the tubes takes the heat of the room away.  A fan behind the tubes blowing into the room, helps the process along.  

When the tubes warm up the refrigerant travels to another region of tubes.  There the refrigerant condenses.  This place is called, reasonably, the condenser. It's connected to the cold tubes but on the outside of the window. As you may recall, condensation releases heat.  Another fan helps blow the warm air away, The refrigerant travels back through the compressor and the whole cycle begins again. 

So, that helps explain the noises. The compressor is an electrical device, probably not well shielded for sound, and designed to work non-stop for months or years. The refrigerant is gurgling through the tubes, creating a lessor drumbeat of noise.The fans may be creaky or unbalanced.  The axles that the fans spin on may be a bit warped or twisted.

The cover of the air conditioner is made out of relatively flimsy plastic that vibrates when the compressor, fans, condenser coils, and other relays, switches, and valves click on and off. 

Jamming something, like a wood shim, between the case and the wall or window frame might deaden the vibrations. Or you could wear earplugs -- or just get used to the noise.  

Modern houses, built in the past 50 years, put the compressor outside in a small enclosure. The less noisy parts are inside the house. 

Several decades ago Albert Einstein, the atomic genius, and a an acquaintance,  Leo Szilard, future father of the hydrogen bomb, developed a novel  refrigerator that used heat to create cold. It consisted of three loops containing ammonia, butane, and water.  The device required no electricity.  Einstein was apparently interested in air conditioning due to a accidental release of refrigerant that  reportedly killed a family in Vienna in 1926.  

Einstein and Szilard refrigerator 
diagram

The descendants of the Einstein-Szilard refrigerator are now used in nuclear power plants, where the absence of moving parts more than compensates for the air conditioner's complexity.  

If price were no object could a quiet air conditioner be produced? A quieter one, sure.  It would be packed with noise-dampeningn foam, contain a carefully designed and balanced compressor, and equally precise fans, belts, tubing and so on. The quiet ar conditioner would probably cost as much as a new car, roughly speaking.  

As the greenhouse effect heats Earth to levels unprecedented since pre-history, think about how air conditioning works, about Einstein the inventor, and about how how delicious the sound of the window air conditioner clunking and buzzing away.  

Some air conditioners are quieter than others