Hypernasal voice - kaibisei

…(2) Articulation function A voice with a blocked nose is called a closed nasal voice, and mu becomes bu, nu becomes de, and ng becomes gu. A voice with too much nasal sound is called an open nasal voice, and bu sounds like mu, nu sounds like de, and gu sounds like nu.
[Nose abnormalities, illnesses]
It is well known from experience that colds and other conditions can cause rhinitis and stuffy noses, and that nosebleeds can occur for a variety of reasons, but one nasal abnormality that is easily noticeable from the outside is red nose (rosacea).

*Some of the terminology that refers to "hyponasal voice" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…(2)構音機能　鼻が詰まった声を閉鼻声といい，〈ム〉が〈ブ〉，〈ヌ〉が〈デ〉，〈ング〉が〈グ〉と変化する。鼻に音が抜けすぎる声を開鼻声といい，〈ブ〉が〈ム〉，〈ヌ〉が〈デ〉，〈グ〉は〈ヌ〉に聞こえる。
［鼻の異常，病気］
　風邪などで鼻炎や鼻詰りを起こすことや，いろいろな原因で鼻血のでることは経験的によく知られているが，外部からでもすぐわかる鼻の異常としては赤鼻(酒皶（しゆさ）)がある。…

※「開鼻声」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報