Apple and Google are temporarily blocking workers from listening to voice recordings captured by smart speakers and virtual assistants.
Following Guardian report that third-party contractors used by Apple had heard people having sex and discussing private medical information.
Siri and other services may activate by mistake after mistakenly picking up sounds that they misinterpret as “wake up” words.
Apple said this decision would affect users around the world.
Google suspended the practice in the EU on July 10 but only publicly confirmed it.
Amazon – which also uses staff to transcribe some recordings – did not comment.
Technology companies are using their staff to “classify” voice recordings to improve the accuracy rates of their virtual assistants in processing requests – and take steps to anonymize the source.
Google, for example, distorts the recording before it is listened to to hide the user’s voice.
However, many members of the public were not aware of this practice until the Bloomberg news agency reported the fact earlier this year.
“We are committed to providing an outstanding Siri experience while protecting user privacy,” Apple said in a statement, “
We are conducting a thorough review, but we are suspending the Siri rankings globally.”
The company added that, in the future, users’ voice recordings would not be included in the ranking process, unless they choose to participate.
The German data protection commissioner in Hamburg has also opened an investigation on Google about the practice with which the research enterprise cooperates. .
Voice recognition assistants presented a “very high risk” from a privacy perspective, the regulator said in a press release.
“The use of voice assistance systems must be transparent so that users can obtain informed consent,” added Commissioner Johannes Caspar.
Google has stated that it has already stopped transcribing voice recordings and will continue to do so for at least three months.
A spokeswoman for the company said Google was “in touch” with the data protection commissioner in Hamburg.
“We do not attach audio clips to user accounts during the review process and only perform revisions for about 0.2% of all clips,” she added.
BBC News asked Amazon if it also planned to suspend speech monitoring.
In June, Dave Limp – the executive responsible for Alexa – said that only a “tiny fraction of 1%” of voice recordings had ever been heard by humans.
But he conceded that the terms and conditions of the company could have been clearer about this.