Fricative are often a source of confusion for English learners.

摩擦音让很多英语学习者感到困惑。

First, when the thickened layers of the pericardium rub up against each other - it creates a friction rub which can be heard on auscultation.

当增厚的两层心相摩擦，可在听诊时闻及心摩擦音。

These are all fricatives, the sounds are coming out slowly and you hear this friction sound.

这些都是摩擦音，声音慢慢地发出你会听到摩擦声。

To be clear, fricatives mean there is a partial obstruction in the air stream.

清楚地说，摩擦音指的是气流有一部分被阻滞。

So, to make the th sound you already know, I hope that the tongue needs to be outside, and the air has to pass between the tongue and teeth in order to create this friction sound.

所以，要发出你已经知道的 th 音，需要舌头在外面，空气过舌头和牙齿之间，才能发出摩擦音。

It usually results in a friction rub, as well as ECG changes like ST elevation and PR depression, followed by T wave flattening and inversion.

常表现出心摩擦音，以及ST段抬高和PR段压低等心电图改变，继之呈现T波低平和倒置。

In today's program, we will explore fricatives.

在今天的节目里，我们要探索摩擦音。

Another type of consonant is a Fricative.

另一种辅音是摩擦音。

Next are the fricatives, where two parts touch.

接下来是摩擦音，其中两个部位接触。

Our tongue sticks out between the teeth, which is why it's called a dental fricative and we're vibrating sound.

我们的舌头伸到牙齿之间，这就是为什么它被称为齿音摩擦音，同时发出振动音。

The rule reads: a voiced fricative is transformed into the corresponding voiceless sound when it appears before a voiceless sound.

规则如下：浊摩擦音出现在清音之前时， 将转换为相应的清音。