Sometimes I spoke to her in a harsh tone.

For your reference only.

too high sounding

you speak harshly to her

找到了英语母语者说出的类似的句子，见一下链接。

句子应为一般现在时，因为这说的是通常的情况。如果这是纯粹的回忆，也可以用过去时。
另外，原文句子并无明确的比较级的含义，“重了一点”作为口语表达，用harshly就够了。


5 Thoughts Before You Speak Harshly - Dr Carol Ministries
https://www.drcarolministries.com/5-thoughts-before-you-spea...
Before you speak harshly to your spouse, these thoughts can help you be helpful instead. ... It takes real emotional and spiritual maturity to pause before speaking, and to consistently use our words for good and not for ill. (See James 1:26 , 3:5 ) ... Or I forget to let him know when I've safely arrived at the hospital. Of course ...

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Note added at 1 hr (2018-02-27 21:42:17 GMT)
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At times, I speak harshly to her.

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Note added at 2 hrs (2018-02-27 23:18:52 GMT)
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At times, I speak a little harshly to her.

Googling "speak a little harshly", you will see a lot of hits. See below.


The pathway of safety: or, Counsel to the awakened
https://books.google.com/books?id=Qi83AAAAMAAJ
Ashton Oxenden - 1861 - ‎Religion
has only lately been awakened, is very apt to judge a little severely and to speak a little harshly, of those who do not think and feel just as he does. He seems to forget the condition that he himself was so lately in. And although he knows himself to be a monument of God's marvellous patience, he is himself impatient towards ...
The Pathway of Safety; or, Counsel to the Awakened
https://books.google.com/books?id=Hu1mAAAAcAAJ
1859
has only lately been awakened, is very apt to judge a little severely and to speak a little harshly, of those who do not think and feel just as he does. He seems to forget the condition that he himself was so lately in. And although he knows himself to be a monument of God's ...
Every Other Sunday - Volume 24 - Page 78 - Google Books Result
https://books.google.com/books?id=Hi0rAAAAYAAJ
1908 - ‎Sunday schools
And then she replied in her easy way, "I presume I did speak a little harshly, but I am going to do better soon. But there isn't any hurry about it. New Year's isn't till to-morrow." The child had not meant to speak sarcastically. But Aunt Martha thought it was a sharp thrust at her inability to control her temper. She went out and ...

Sometimes, I sound a tad harsh when I talk to her

我觉得不一定要一定把”口气“给对应地翻译出来。不过，我不反对还有其他、甚至是更好的翻译，包括译出”口气“的译法。

I at times would speak to her with a bit of heavy handed tone.

供参考

When I speak to her I am often a bit on the harsh side.