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Alexa has had a lot of explaining to do. Since Amazon's voice assistant debuted in 2014, the company has convinced millions of people to invite Alexa into their homes. They use it to play music, serve up the news and answer trivia questions. This year, though, the online retailing giant faced a backlash after news broke that human reviewers were sometimes listening to recordings of users' private conversations with Alexa.

Those privacy problems will likely cast a shadow on Amazon's annual product launch, which takes place Wednesday in Seattle. There, the company is expected to unveil the latest devices in its Alexa-powered Echo speaker lineup.

Alexa has dominated the smart speaker race against Apple's Siri and Google Assistant. Echo devices have flown off Amazon's digital shelves, particularly during Prime Day, when the company's hockey-puck-shaped Dot topped the sales charts. Now, of the 76 million smart speakers perched in US homes and businesses, 70% are Echo devices, according to Consumer Intelligence Research Partners.

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Amazon isn't alone in trying to address privacy issues. Google, Apple, Microsoft and Facebook have also admitted to listening in on recorded user conversations with smart assistants. Amazon has responded by introducing a series of privacy-friendly features in hopes of allaying consumers' concerns.

"They've at least been responsive to the issue," said Bret Kinsella, a voice and AI researcher and founder and editor of Voicebot.ai. "Whether everyone thinks it's responsive enough is another issue."

Though they capture most of the attention, Echo speakers aren't the only gadgets Amazon is expected to launch. In recent months, rumors have circulated that the company is working on Alexa-powered wearables, such as glasses, and wireless earbuds that resemble Apple's AirPods. The company is also said to be working on a premium speaker that could compete against the Google Home Max and Apple HomePod. Perhaps most intriguing: an Alexa home robot on wheels, which Bloomberg reported in July.

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In past years, Amazon has used the event to refresh its Echo lineup, often adding softer and sleeker designs. It's also broadened Alexa's capabilities and the places it can communicate. Last year, as part of a flurry of new devices and features, it introduced the Echo Auto device to bring the digital assistant into more cars, as well as Alexa Guard, a new home-security feature that can alert users when Alexa hears glass break or a smoke alarm.

Further privacy settings could be announced at Wednesday's event.

"At Amazon, customer trust is at the center of everything we do and we take customer privacy very seriously," an Amazon spokesperson said in a statement. "We continuously review our practices and procedures to ensure we're providing customers with the best experiences and privacy choices. We provide customers with several privacy controls, including the ability to review and delete their voice recordings and microphone- and camera-off controls."

The human reviewer dilemma

The spread of Alexa-powered gadgets means more devices that could be vulnerable to privacy slipups.

In April, Bloomberg reported that human reviewers listened to Amazon Alexa recordings. The reviewers deciphered garbled or noisy recordings and then fed them back to Alexa so it could better understand its millions of users. That's been a common practice in refining voice-operated products, though one most consumers haven't known about. Reviewers didn't have access to the full names or addresses of users.

Bloomberg's reporters uncovered troubling cases, though. In some instances, a reviewer heard a child screaming or a woman singing off-key in the shower. In the months that followed, the situation cascaded across the tech industry. In July, a contractor leaked more than a thousand recordings of people using Google Assistant to a Belgium-based news service. Later that month, The Guardian reported on contractors listening to recordings made by Apple's Siri assistant, including instances of private doctor-patient discussions and people having sex. Last month, Microsoft acknowledged human reviewers could be listening to conversations with its Cortana assistant.

Facebook, never one to miss a privacy scandal, joined the group in August with news of contractors being used to transcribe audio clips from Facebook Messenger voice chats. The contractors ensured text transcripts of those conversations were accurate.

These companies defended the practice, saying it's needed to train voice assistants to personalize responses and understand the difference between similar-sounding words like "Austin" and "Boston." "This is a critical part of the process of building speech technology, and is necessary to creating products like the Google Assistant," Google Product Manager David Monsees said in July, echoing the sentiments of fellow tech companies.

But with privacy scandals popping up online seemingly every day, the public might not be so forgiving.

In May, children's advocates called on the Federal Trade Commission to investigate the child-focused Echo Dot Kids Edition. The next month, Amazon was hit with two lawsuits that alleged the company failed to get children's consent when it records them using its voice assistant. Amazon says it requires parental consent and provides many privacy controls for parents. Also in May, CNET reported that Amazon kept transcripts of Alexa interactions even after people deleted the audio recordings. The company has since fixed this issue.

Consumers who were on the fence before, they may stay away. Blake Kozak, IHS Markit

Amazon and Google say the number of recordings that get reviewed is tiny, a fraction of 1%. Still, the tech giants have changed their policies to soothe concerns. In August, Amazon allowed users to avoid human reviews, with Apple quickly following suit. Facebook halted its review program.

Google two months ago suspended its reviews globally after a German regulator temporarily banned the practice in Europe. Then on Monday, Google apologized for not telling customers clearly how their data was being used and updated its human reviews policies, requiring users to opt in to reviews.

Amazon has also included physical features to protect privacy. The Echo Show 5, a smart display introduced in May, has a privacy shutter that obscures the camera. The Facebook Portal and Google Assistant-powered smart displays have had a similar feature since they launched in 2018.

Amazon also created an Alexa privacy hub on its website and it lets users erase their recordings by saying, "Alexa, delete everything I said today."

Pushing Alexa into the future

Amazon doesn't appear to be slowing down, and it's given Alexa new capabilities that could gobble up more consumer data.

For example, the company in December added the ability for software developers to use real-time location tracking in their Alexa apps so someone could use the voice assistant to find a nearby coffee shop or gas station, similar to how they'd use Siri or Google Maps. Consumer permission is required to turn on this feature.

David Limp, Amazon's hardware chief, said in June that having Alexa register a user's emotion could be useful, though he avoided mentioning any future products that may use such a feature. Google's new Nest Hub Max uses a new facial recognition technology called Face Match, which can show you your photos, calendar and texts when it sees your face.

It's possible some of these concepts -- location tracking, emotion sensing and facial recognition -- may be mentioned at Wednesday's presentation.

Along with the Echo Show 5, Amazon this year already introduced a new Fire TV Cube video-streaming device, a series of Amazon Fire TV-powered televisions and a new sound bar, so Alexa enthusiasts shouldn't expect another refresh of those devices at the event.

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But people can expect some more-experimental items to show up Wednesday, like the Alexa-powered wall clock and microwave from last year, along with revisions to the core lineup of Echo speakers. As far as privacy features go, Amazon may bolster its "local voice control" settings, allowing an Echo speaker to handle more requests on its own, without having to send any recordings or data to Amazon's servers.

Blake Kozak, an IHS Markit smart home analyst, said he'd expect Amazon on Wednesday to add more privacy shutters on its smart displays to catch up to its rivals, and to potentially discuss Alexa's new HIPAA-compliant health apps to help bolster the voice assistant's reputation for handling sensitive data.

"Consumers who were on the fence before, they may stay away," Kozak said about users' reactions to this year's privacy issues. "But consumers that use these devices won't throw them away."

Originally published on Sept. 22.

Update, Sept. 23: Adds news of Google's changes to its human reviews.