What was that awful sound?

That’s what one of my friends asked another after recently visiting Lebanon’s downtown pedestrian mall. I heard the question again the next day, after a different group had gathered on Park Street.

My friend who works downtown had the answer right away, pointing to a Feb. 7 public memo in which city officials announced the installation of sound machines meant to “deter crows from gathering and roosting in the trees.”

“If you happen to hear a strange noise in the area of the Lebanon Mall, please be aware it is the deterrent device in operation,” the memo said.

But whereas the city characterized the device’s sound as “faint,” my friends recounted a sonic assault: ongoing high-pitched beep-beep-beeps that they found both irritating and, to those who didn’t know the source, bewildering.

I had to hear for myself. For starters, I wanted to square these differences in description. I also like crows, who gather in groups called murders. They are amazing creatures, capable of recognizing human faces, teaching complex tool use to their young and a long list of other fascinating skills, as detailed in Jennifer Ackerman’s “The Genius of Birds.” The New York Times recently wrote about crows’ capacity for multigenerational grudge-holding and vengeance (watch out, Lebanon). Across much of the country each winter, mixes of local crows and migratory travelers come together to form huge nightly roosts for the season, as Maine Public Radio put it, “to stave off predators like the Great Horned Owl, stay warm, look for mates and possibly share some news.”

I was surprised and saddened that we’d take drastic steps to scare crows away, especially since those measures seemed to scare off people, too. Soon, though, I was metaphorically eating a bit of crow, as I learned that balancing the intrusion of noise against the hazards of bird poop is no easy task.

First, a trip to Colburn Park. After lunch on Sunday, I couldn’t detect a peep as I walked along the park’s far edge, across from Lucky’s Coffee Garage. But as I kept walking, there it was. Or was it? What the heck was I listening to?

The sound became clearer across from the entrance of Rogers House. As I moved into the crosswalk toward City Hall, it was unmissable. And in the walkway between the two brick buildings, it was overpowering: the rapid cadence of hungry baby birds, the piercing octave of a smoke alarm, the tooth-grinding frequency of a broken TV, and, especially because I couldn’t locate the physical origin, an eeriness that evoked the descent of an alien spaceship.

Not everyone can hear the devices, including a woman I spoke to as she headed toward Rogers House. I told her that I didn’t see the big deal with the crows. They’re all right, she sighed, but they squawk a lot.

Turns out, they also poop a lot. There’s still evidence on some of the windows along the pedestrian mall in the form of vertical white streaks. They were pointed out to me on Monday morning by Robert Murphy, who was headed home on his bike. The 53-year-old has lived in Lebanon all his life and sees the roosts every winter. He agrees with the city that crow poop is a real problem, yet found this solution “stupid.”

Murphy’s main issue is not with the deterrent devices themselves, which produce a sound he considers “annoying,” but with their non-stop nature. The birds roost only at night, he observed. Why subject humans to this cacophony during the day?

I was ready to go one step further than Murphy: Leave the crows alone! Throw these noisemakers in the trash! But when I called up Craig Gibson, a man who loves crows so much that he runs a crow-tracking website and traveled nearly two hours from Winchester, Mass., in January to see Lebanon’s murder in flight, his support for deterrent measures — though qualified — surprised me.

Gibson’s site, Winter Crow Roost, primarily tracks an annual roost in Lawrence, Mass., where some 15,000 crows “politely find trees to roost in where they’re not causing a stinking mess,” he told me. Many of Lebanon’s thousands of crows, meanwhile, have been perching and pooping in trees above cars and walkways, leaving a smelly disaster zone that city workers must frequently clean. Rude!

Even so, I remained unconvinced about the noisemakers on Tuesday as I dialed Rick Brown, Lebanon’s assistant director of Public Works, who had left for vacation thinking he’d addressed a barrage of complaints about crow poop and returned this week to a new barrage of complaints (though fewer, he said) about the solution.

The detritus crows leave below their roosts can spread disease to people, the Washington Department of Fish & Wildlife wrote in a 2005 pamphlet. It noted that health risks associated with birds “are often exaggerated,” and an infection control officer told the CBC that hand-washing should address the mild risk. Still, when Brown described “every inch” of the mall’s handrails and other public accessways previously covered in guano, it was hard to argue with his characterization of a “health hazard.”

“It was bad,” he said.

The city spent about $1,400 on devices called BirdXPellers, he said, and they seemed to be working. With speakers located atop City Hall and on lamp posts along the mall, they didn’t draw many complaints at first, perhaps because fewer people were outside when it was colder.

The noise devices are still “kind of a learning curve for us right now,” Brown acknowledged on Tuesday. Just that day, he said, the city turned down the volume in response to the complaints. (He wasn’t sure about the levels the city was using, but the BirdXPellers’ advertised maximum is 105 to 110 decibels within one meter, which is comparable to a car horn, at a frequency of 3 to 5 kilohertz.) Brown also ordered timers that will allow the city to limit the noise to overnight hours, he said.

Gibson, the crow enthusiast, said it shouldn’t take much to deter the nightly roost: just an hour or 90 minutes of noise starting at sunset. Anything more, he said, is “totally unneeded,” in part because crows have terrible eyesight in the dark and stay put overnight. Since crows’ roosting patterns are seasonal, Gibson said, the solution can be seasonal, too. Lebanon’s winter roost is likely made up of roughly 20% Upper Valley breeding crows and 80% migratory birds, he said, who will soon head northeast.

When the roost starts forming again in the fall, I hope we limit the deterrence as much as possible. Replacing a naturally annoying situation with an artificially annoying one evokes some of our worst instincts. Haven’t we all been awed by a miles-long sky river of thousands of crows flocking across the valley before dusk, backdropped by a pinkish winter sunset?

One place or another, they’re going to have to poop.

Maggie Cassidy is a freelance writer, the former editor of the Valley News, and the former managing editor of VtDigger. She lives in White River Junction.