An Amazon Echo.  (David Ryder for The Washington Post)

How often do Amazon.com's Echo devices misinterpret human commands, and, say, start recording private conversations without permission? Two senators want to know.

In a letter dated June 11, Sens. Jeff Flake (R-Ariz.) and Christopher A. Coons (D-Del.) pressed Amazon's chief executive, Jeffrey P. Bezos, for answers on the smart speaker's listening habits, and what the company is doing to protect the privacy of its customers, who often place the Alexa-powered devices in the most intimate spaces in their homes. The letter was first reported by Wired. (Bezos owns The Washington Post.)

The senators, who lead the Judiciary subcommittee on privacy, technology and the law, framed the letter around a recent incident involving a family that discovered that their Echo had recorded a private conversation and sent it to a random person in their contacts. The person happened to be the husband's employee and the conversation happened to be about wood flooring. The incident highlighted the risks of installing Internet connected microphones in the home.

At the time, Amazon said the Echo woke up when it heard a word that sounded like “Alexa.”

“The subsequent conversation was heard as a ‘send message’ request. At which point, Alexa said out loud ‘To whom?’ At which point, the background conversation was interpreted as a name in the customer's contact list,” Amazon said. 

The senators took issue with Amazon's explanation for what happened. “Reportedly, Amazon did not attribute this incident to a device malfunction or a glitch in the system,” they wrote. They acknowledged that Amazon has said it is considering options to make these unlikely string of events less likely to occur, but they wrote, “we are concerned that the device in this instance performed precisely how it was designed. Without prompt and meaningful action we expect that additional  instances like the one summarized above will happen again.”

The letter to Bezos contained six questions. The senators asked for the number of complaints the company has received about misinterpreted commands; the reasons Amazon might use and retain customer voice data captured by Echos; and what policies are in place to prevent the misuse of voice data and to prevent future episodes where conversations are shared without a customer's consent. The senators also asked more granular questions about Alexa and Echo's protocols for activation, recording voices, and access to third party developers.

Amazon did not immediately respond to a request for comment.

According to the Pew Research Center, roughly half of U.S. adults use digital voice assistants and about 8 percent use stand-alone devices such as the Echo.

Amazon, like Google, which offers its own smart speaker, keeps  a copy of every conversation its users have with the device. The recordings offer some transparency and help improve the companies' voice-recognition and artificial intelligence systems. Users can listen to and delete these past recordings in the Alexa app and on Google's user activity site.