hums and haws

今日の表現もJohn McEnroeについての記事からです。
When I ask what is the single most important thing he learnt from therapy, McEnroe hums and haws for a few moments before saying that he doesn't think there is one. "I'm not saying I didn't learn something, but I can't say it was one specific thing where a lightbulb went on...
"hums and haws" は慣用句の様です。　"haws" は知らない単語ですが、"hums" はハミングの "hum" の様なので、"hums and haws" は軽く唸ったという感じでしょうか？辞書を見ます。
・American Heritage Dictionary: To be hesitant and indecisive; equivocate: "a leader who cannot make up his or her mind, never knows what to do, hems and haws" (Margaret Thatcher).
"hums and haws" で見つけたのは上の辞書だけですが、この表現は　"hummed and hawed" 、"hemmed and hawed "、 "hems and haws" とも言われ、皆同じ意味の様です。
・Wiktionary: (UK, idiomatic) Procrastinate and take a long time before doing something or taking a decision.: We hummed and hawed before buying this house.
・Collins Dictionary: hesitate, waver, dither, vacillate, be indecisive, falter, swither (Scot. dialect) My mother hummed and hawed at first, then she agreed.
・Cambridge English Dictionary: to be uncertain and take a long time deciding something: We hummed and hawed for months before actually deciding to buy the house.
・Vocabulary.com: utter `hems' and `haws'; indicated hesitation: “He hemmed and hawed when asked to address the crowd”
唸り声が物理的に出るわけではないのですね。