Yes, it is possible for someone to overhear a conversation in the background while talking on a cell phone, especially if certain conditions are met. This phenomenon is known as "crosstalk" or "sidetone."
Crosstalk occurs when the person you are talking to on your cell phone's microphone picks up sounds from the surrounding environment, including the voices or noises of people who are physically close to the person you are talking to. This can happen if the person on the other end has their speaker or microphone volume set too high, or if they are using a hands-free device that captures more ambient sounds.
Here's how it might have happened in your friend's case:
Speaker Volume: If her husband was talking nearby and had his phone's speaker volume set high, his voice could have been picked up by her niece's phone microphone, causing your friend to overhear his comment.
Hands-free Device: If her niece was using a hands-free device like a Bluetooth headset or speakerphone, it could have captured the surrounding sounds more effectively, including her husband's comment.
Proximity: If her niece and her husband were physically close to each other while on the call, the chances of crosstalk would be higher.
Microphone Sensitivity: The sensitivity of the phone's microphone could also play a role. Some devices may have more sensitive microphones that pick up sounds from a wider area.
It's worth noting that crosstalk is more likely to happen in quieter environments, where background noises are less prevalent. In noisy environments, the ambient sounds may not be as noticeable, and crosstalk becomes less likely.
To avoid crosstalk, people can use headphones, ensure their speaker volumes are at appropriate levels, or use noise-canceling technologies when talking on the phone. However, in some situations, crosstalk can still occur, especially if the devices or settings are not optimized to prevent it.
If your friend wants to prevent this from happening again, she can ask her niece to adjust her phone settings or use headphones during calls to reduce the chances of crosstalk.