The [ ？] sound is a front vowel， which for me means it feels like
it comes more from here ， aa ， than from here ， ah. It's a bit difficult
to explain， so I am going to explain it in terms of another vowel， and
that is the [e] as in "pet" vowel. Both of them ， eh ， aa ， you can
see my tongue is up ， as opposed to ah ， "father" ， where you can see
the dark space in my mouth. Aa， all you see is tongue. So it's coming
up， and making a bit of a wall ， so that you see this part. The way
it's different from the eh vowel， which is more like this， eh ， aa ，
is that the tip of the tongue is not touching underneath the teeth as
it is in eh. This part of the tongue is a little more vertical and more
spread for me ， which feels like it creates more space back here. Aa ，
aa. Also the jaw has dropped a little bit more than on eh. Aa ， aa. And
the last subtle change that happens is here. It's easy to see. The lip
comes up just a little bit. Pets， pats.

    [ ？] 是一个前元音，它和[e] 音的共同特点是发音时舌头要抬起，这和发
father中的[a：] 音不同。发[a：] 音时可以看见口腔中的黑影部分，但是发[ ？

    ] 时只能看见舌头。因为舌头抬起形成了一座“墙”。

    [ ？] 与[e] 不同之处在于：发[e] 时舌尖触及下面的牙齿，但是发[ ？]
时并不触及；发[ ？] 时舌根部分更加垂直、更加舒展，感觉在后部制造出了更
多空间；另外发[ ？] 时下巴下移的位置要比发[e] 时更多一点，而上嘴唇则要
比发[e] 时上移得更多。

    Sample words：

    habit 习惯

    understand理解

    Sample sentence ：

    Cameron is mad about fashion. 卡梅隆痴迷于时尚。