These are called "distortion products" and happen at multiples of the fundamental test tone.

这些称“畸变产品”并且发生在根本测试口气的倍数。

youdao

We called a line with a test tone and started covering up the phone (note, we cannot be sure this line is toll free, but we risked it).

我们用测试语气拨打了一个号码然后开始覆盖住手机(PS：我们不确定那个电话是免费的，但是我们还是冒险了)。

youdao

I thought back to the periodic interruption I'd grown up with in the mid-20th century — the ear-invading tone that was part of the radio and TV "emergency broadcasting system" test.

是我回想起我所成长的20世纪中页的耳熟能详的周期性断电，耳边回荡着“备用广播电视应急”测试的声音。

youdao

President Clinton, whose cynicism never loses its power to astonish, put on a long face and, with that tone of sincerity that betokens his tendentiousness, lamented that the Comprehensive Test Ban Treaty had become tangled in politics.

CENTERFORSECURITYPOLICY: Center for Security Policy | Politics and the Test Ban Treaty, By George F. Will, Newsweek, 20 October 1999

From the outside, improvements look cosmetic a friendlier tone in bills, for example, and a much-publicised customer hotline, which in a recent test played soothing music for a few minutes before disconnecting abruptly.

ECONOMIST: Deutsche Telekom