Warning: This story discusses domestic violence.

On Wednesday, every cellphone in the United States will emit a distinct, grating sound.

The noise, an emergency notification from the Federal Emergency Management Agency (FEMA), is a test of the National Wireless Emergency Alert System, which is meant to alert every TV, radio and cellphone in the country in the event of a national crisis.

For many, the disturbance will be nothing more than annoyance. But for survivors of domestic abuse and those in risky situations, the safety test could lead to danger.

The test alert is set to blast out on Wednesday, Oct. 4, at 2:20 p.m. EDT, 1:20 p.m. CDT, 12:20 p.m. MDT and 11:20 a.m. PDT and will last about a minute, similar to an Amber Alert or weather alert.

It will be sent only once; cellphones will also get a vibration and a text message. TVs and radios will experience an interruption in broadcasting for reading of a similar message. These messages will clarify that the notice is simply a test, the first of its scale since 2018.

What to know about emergency alert test:When is the big emergency alert test? Expect your phone to ominously blare Wednesday.

Hidden devices and their importance

For at-risk people who keep and use secret communication devices for safe contact with the outside world, the test could have consequences. Domestic violence organizations issued warnings locally and nationally ahead of the test to caution those who may be at-risk and relying on hidden devices.

The National Network to End Domestic Violence (NNEDV) issued one such warning last week, noting that settings that are usually effective in blocking certain notifications like Amber Alerts will not work for this specific notice. While people who rely on hidden devices may have safeguards that work the rest of the year, such as keeping all normal notifications silenced and toggling settings to block public alert sounds, it is important that they know these usual measures will not work this time around.

"For survivors of intimate partner violence or domestic violence, having a hidden device is essential for various reasons," Audace Garnett, a technology safety project manager at NNEDV, told USA TODAY.

"It acts as a lifeline, allowing survivors to use it to make emergency phone calls to connect with support networks for services. Additionally, they can use it for privacy reasons. They can use it as an alternative means of communication," Garnett said. "If the abuser is monitoring their primary device or if that primary device has been compromised, they can now use this hidden phone as an alternative means of communication."

A hidden phone can not only keep someone living in an unsafe situation in contact with outside friends and family but also be used for working on safety plans with advocates or, in a worst-case scenario, contacting emergency services.

"There are features within your device where you can go into your settings and you can disable notifications. However, this current alert that we're going to be receiving … you cannot disable that," said Garnett. "So that's the whole cause of concern because if the survivor's device is on, it could potentially (be found) and make things escalate."

The discovery could also lead to a confrontation or an escalation, putting the victim in harm's way, Garnett said.

Hidden cellphones: Tips for safety with Wednesday's test

Investigators hone in on Liberty U:Feds say Liberty University created 'fear of reprisal' for sexual violence survivors

In the case of Wednesday's test alert, silencing your phone or changing settings to block notifications will not work. In this case, the best course of action is to turn the phone off completely – do not put it on airplane mode or otherwise leave the phone on.

"We're suggesting that the survivor just turn the device off during the scheduled time (Wednesday)," said Garnett. "Just keep the device turned off. If you do have any phone calls that you're going to schedule, do it another time. Do not take the risk by having your device on."

While this tip will lower the risk of discovery during this specific event, there are steps to protect hidden devices year-round.

First, go into your phone's settings and opt out of certain national notifications such as Amber Alerts and weather warnings. Ffor Android phones go to Notifications, then Advanced Settings, then Wireless Emergency Alerts; iPhones have Government Alerts at the bottom of Notifications; you can also turn on or off alerts with a keypad call if you are using iOS 15.3 or earlier.

Likewise, it is important that your hidden device not be in any way connected to primary devices that an abuser already knows about. These means no adding the separate phone to the cloud, sharing contacts or signing into online services with your ID.

Securing access to accounts such as email, setting up two-factor authentication and using a VPN to hide your location can also be used as year-round tactics for making sure what you want to keep private stays private. NNEDV has also established a guide with internet security company Norton that offers step-by-step instructions on keeping hidden accounts and devices secure.

For those at risk, it's important to remember there is help available. "They're not alone and what they're going through is not their fault," said Garnett. "The National Domestic Violence Hotline operates 24/7 and over 200 languages are spoken on there."

If you are a victim of domestic violence, the National Domestic Violence Hotline at 800-799-7233 allows you to speak confidentially with trained advocates online or by the phone, which they recommend for those who think their online activity is being monitored by their abuser. They can help survivors develop a plan to achieve safety for themselves and their children.