At Mosul prison and Camp Nama, it came from boomboxes. At Camp Cropper, in Baghdad, wall-mounted speakers. At other places, like Camp Romeo, a punishment area within Guantanamo, it came from special conical speakers rolled in front of a prisoner's cell.

Loud music. It's the harsh background noise of the US war on terror. The phrase itself—"loud music"—appears 17 times in the ​recently declassified executive summary of a still-classified CIA "torture report." But while it's been no secret that the US deployed music across an archipelago of detention centers, black sites, and prisons, to disorient and break the will of detainees, what even is "loud"? And how loud is loud enough?

According to ​a footnote in a 2005 US interrogation program memo, the CIA keeps "detention conditions" at every one of its detention facilities, where detainees are subjected to "white noise/loud sounds (not to exceed 79 decibels)" during portions of interrogations. The 2005 memo also notes that the Occupational Safety and Health Administration figures "no risk of permanent hearing loss from continuous 24-hour-per-day exposure to noise of up to 82 decibels."

There is currently no international law on the books on just how loud is too loud when it comes to either interrogational or punitive torture. Suzanne Cusick, a New York University music professor who researches acoustical violence in contemporary war, told me that in the 1970s an international ruling was filed against the use by the British in Northern Ireland of a suite of techniques, including ​sleep deprivation, forced standing, exposure to noise, and continuous white noise, and that today, various human rights organizations hope to establish research-based regulations on sonic warfare.

That's what we have to go on, for now. The thing to keep in mind, though, is that "decibels need to be correlated with the amount of time a person is exposed to the sound at a particular decibel level," according to Cusick, who told me about the time she interviewed a man—he wished to remain anonymous, however he is one of the 119 people described in the Senate report as tortured by the CIA and its contractors—detained at the CIA's clandestine COBALT prison, otherwise known as the "Salt Pit," in Afghanistan.

He said he'd been held there in the dark, for a month, while near-continuous white noise reverberated through COBALT's corridors and cells. "He told me it seemed like a tape, or something," Cusick said. It would play for about 45 minutes before going silent for about seven seconds, at which point the prisoners would try calling out to one another. Then the loud music would start up again.

Interrogation? Punishment? You decide.

From Standard Operating Procedure. Apparently, detainees show a marked aversion to country music.

Playing the same songs, typically loud metal or hip-hop, on repeat, sometimes for days on end, is a cornerstone of ​a standard operating procedure described by the Department of the Army as "futility": "[The] collector convinces the source that resistance to questioning is futile. This engenders a feeling of hopelessness on the part of the source."

It's about breaking someone. As such, Cusick believes looping, loud music and sound have not been "trivial" components of the US' counterterror program, but intrinsic to it.

"'Loud music' as used in US-managed detention facilities is not only psychological torture," she said. "Sounds are the audible manifestation of waves moving through air, and those waves necessarily produce physical effects." These effects can range from the immediate sensation of having been beaten, Cusick added, to the development, or exacerbation, of hypertension and hearing loss long after the final clangs of the "acoustical beating" ring out.

What sort of sounds are we talking about? The CIA's mixtape, at least what we know, is truly eclectic, from Bruce Springstein's "Born in the USA" to Christina Aguilera's "Diirty," Barney the Dinosaur's "I love You," Deicide's "Fuck Your God," Metallica's "Enter Sandman," David Gray's "Babylon," Queen's "We Are the Champions," Rage Against the Machine's "Killing in the Name Of," and also songs by Meat Loaf, Aerosmith, AC/DC, Marilyn Manson Drowning Pool, 2Pac, Dr. Dre, Eminem, Britney Spears, and Matchbox 20.

There's ​no Rorschach, although it's been reported that detainees exhibit a marked aversion to country.

When it stops, it's like a beating stopped.

Of course, the US has been waging war with sound, in one way or another, for decades. Cusick said the theoretical grounding for sonic warfare is ​an internal CIA document from 1963, the so-called Kubark report. Even before that, from about the mid-1950s, she added, "loud music" and "noise" resistance was part of ​Survive-Evade-Resist-Escape, a US special forces training program.

Later, in 1988, US security personnel had recordings to drown out Manuel Noriega, the ousted Panamanian dictator, who'd holed up in the Vatican Embassy, and also against the Branch Davidians, before torching their compound in Waco, Texas. Which is to say, 17 instances of "loud music" in a declassified executive summary of a forthcoming torture report is not news. The only difference now, according to Cusick, is that the US has finally admitted "to doing what everyone already knew we did."

But then, how loud is too loud? That's hard to say. Because how, really, can anyone know? We all experience pain differently.

"I assume that the effect on human beings of loudness may be similarly difficult to measure and calibrate," Cusick said, because of a whole complex of individual differences.

One also must consider the duration of loud music and any other stimuli in the mix. How does that affect the experience of loudness? For context, 79dB, supposedly the CIA's sonic limit for interrogational and punitive acoustic beatings, is roughly that of a washing machine or vacuum cleaner. Based on her discussions with the aforementioned unnamed Salt Pit prisoner, Cusick believes the sound there was probably kept right at the 79dB threshold, albeit "tremendously magnified" in prisoners' consciousnesses by virtue of isolation and continual black-out conditions.

In that context, then, 79dB was indeed "too loud." Or rather, from the perspective of the CIA and its contractors, precisely loud enough to break a man.