Walmart has patented surveillance technology that would allow it to spy on employees’ conversations with customers and use the audio to measure workplace performance.

The patent for “sound sensors” that could be installed at checkout is the latest example of controversial workplace surveillance technology and automated systems that purport to quantify and increase employees’ productivity. The filing comes at a time in which the US retail giant is facing growing competition from Amazon, which completed a $14bn acquisition of Whole Foods last year.

The patent filed this week described a system of sensors “distributed throughout at least a portion of a shopping facility”. Audio of both workers and customers could potentially be used to determine “if employees are performing their jobs efficiently and correctly” and aid in increased “cost savings” and “guest satisfaction”, the document said.

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Walmart said in a statement that the patent is a “concept that would help us gather metrics and improve the checkout process by listening to sounds produced by the bags, carts and cash registers and not intended for any other use”, adding: “We file patents frequently but that doesn’t mean the patents will actually be implemented. We’re always thinking about new concepts and ways that will help us further enhance how we serve customers.”

The system, the filing said, could record “beeps” on the scanner to measure the number of items purchased; the “rustling of bags” to determine the number used; the sounds of “guests talking while waiting in line” to measure the length of the wait; and the “audio of conversations between guests and an employee” to gauge whether workers were greeting guests.

In recent years, there have been escalating concerns about employers monitoring workers, with critics questioning the effectiveness of this technology. Some research has suggested that excessive monitoring could lead to decreased efficiency, as BuzzFeed reported.

There have also been growing criticisms about the surveillance leading to potential privacy and labor rights’ violations. Walmart has long faced criticisms over its treatment of employees, including complaints about wages, working conditions, anti-union tactics and discrimination.

Walmart has been under increasing pressure to slash prices following Amazon’s purchase of Whole Foods.