How to tell if a なり is the なる form or if it is the hiragana form of a word?

Question

I am uncertain if the bolded なり below is the hiragana form of the kanji 鳴り 'ringing, sound' or if its the なる form for the そぞろ. (which would come out as 'to become restless/ to become on edge (and unable to concentrate )/ to become distracted').

Any help provided for me (and others) to learn how to discern which it is would be greatly apricated.

ついつい気がそぞろになり、ラジオの放送が耳を[素通]{すどお}りしてしまった。

Answer 1

～なり as a grammatical construct comes from the word なる ("to become"). It's often used to join two phrases with a logical sequence to each other.

In your example, the first phrase is

「ついつい気がそぞろになる」

"I found myself getting distracted"

→　As a result of the first phrase:

「ラジオの放送が耳を素通りしてしまった」

"the radio broadcast went in one ear and out the other."

Another way this is used is to provide a non-exhaustive list of examples. For example:

メールなり電話なりで、お気軽にご連絡ください。