3 sentences

1. 他的发言语调平板，听起来很乏味。

   tā de fā​yán yǔ​diào píng​bǎn, tīng qi​lai hěn fá​wèi.

   His speech was delivered in a flat tone and sounded very dull.

   Source: Dong Chinese Dictionary

2. 他用一种不友好的语调拒绝了我的请求。

   tā yòng yī zhǒng bù yǒu​hǎo de yǔ​diào jù​jué le wǒ de qǐng​qiú.

   He refused my request in an unfriendly tone.

   Source: Dong Chinese Dictionary

3. 学习英语时，掌握正确的语调非常重要。

   xué​xí Yīng​yǔ shí, zhǎng​wò zhèng​què de yǔ​diào fēi​cháng zhòng​yào.

   It is very important to master the correct intonation when learning English.

   Source: Dong Chinese Dictionary