arcane, bated, blurred, breathy, cabalistic, censored, choked, choking, classified, close, closed, concealed, croaking, crushed, cryptic, damped, dampened, dark, dead, deadened, drawling, drawly, dull, dulled, dysphonic, enigmatic, esoteric, flat, guttural, harsh, hawking, hermetic, hidden, hoarse, hush-hush, inarticulate, indistinct, latent, lisping, mispronounced, muffled, muted, muzzy, mysterious, nasal, occult, quashed, quavering, quelled, repressed, restricted, secret, shaking, shaky, smashed, smothered, snuffling, softened, sordo, squashed, squelched, strangled, subdued, suffocated, suppressed, thick, throaty, top secret, tremulous, twangy, ulterior, unbreatheable, under security, under wraps, undisclosable, undisclosed, undivulgable, undivulged, unrevealable, unrevealed, unspoken, untellable, untold, unutterable, unuttered, unwhisperable, velar