Vocal pitch is determined by the fundamental frequency of sound waves produced by the vocal folds, which are twin folds of tissue inside the larynx (voice box). Pitch is lower when the vocal folds are longer, thicker, or less tense, causing them to vibrate more slowly. Conversely, shorter, thinner, and more tense vocal folds vibrate faster, resulting in a higher pitch. A low voice in a female suggests the vocal folds possess characteristics associated with a lower fundamental frequency.
How the Female Voice Normally Develops
The female voice changes during puberty, though less dramatically than in males. Before adolescence, the larynx and vocal fold lengths are similar in both sexes. During puberty, the larynx grows in all individuals, but testosterone in males causes significant enlargement of the thyroid cartilage and substantial lengthening and thickening of the vocal folds.
The female larynx grows to a much lesser extent, with the thyroid cartilage remaining approximately 20% smaller than that of males. Adult female vocal folds are typically 1.25 cm to 1.75 cm long, about 60% shorter than average male vocal folds. This shorter, thinner structure results in the average adult female speaking voice having a fundamental frequency around 200 to 224 Hertz (Hz), significantly higher than the average male range (107 to 132 Hz). A naturally low female voice may indicate a larger laryngeal structure or vocal fold dimensions at the lower end of the typical female distribution.
Hormonal Influences on Vocal Pitch
The most significant biological factor causing a voice to deepen in a female is the presence of androgens, such as testosterone. Androgens act directly on the larynx, causing the vocal folds to lengthen, increase in mass, and thicken—a process similar to male puberty. This thickening leads to slower vibration, which irreversibly lowers the vocal pitch.
Conditions causing an excess of androgens are often associated with voice deepening. Polycystic Ovary Syndrome (PCOS) is a common endocrine disorder involving hyperandrogenism (elevated androgen levels). Women with higher androgen concentrations have a greater likelihood of a deepening voice, along with other symptoms like hirsutism and acne.
Congenital adrenal hyperplasia (CAH) is another condition that can lead to excessive androgen production and subsequent voice changes. Certain medications, such as specific hormonal treatments, can also increase androgen levels, resulting in a permanent lowering of vocal pitch. Once the voice has deepened due to androgen exposure, the structural changes to the vocal folds are generally considered permanent, even if the underlying hormonal issue is later treated.
Behavioral and Structural Causes of Lower Vocal Tone
Not all instances of a lower-pitched or rougher voice are due to hormonal imbalances; several non-endocrine factors can affect the vocal tone. Chronic vocal misuse, such as habitually speaking at an unnaturally low register or using excessive force, can contribute to a perceived lower tone and hoarseness. This behavior can place undue strain on the vocal folds and surrounding muscles.
Structural changes to the vocal folds can also interfere with their normal vibratory pattern, leading to a lower or rougher sound quality. Conditions like vocal fold nodules, polyps, or granulomas are non-cancerous growths, often caused by voice overuse or irritation, that add mass to the folds. This increased mass prevents the folds from vibrating quickly or smoothly, resulting in a lower, often raspy, pitch and a strained voice.
The use of irritants, such as smoking or vaping, can cause Reinke’s edema (polypoid corditis), characterized by swelling and thickening of the vocal folds due to fluid accumulation. This added mass significantly lowers the fundamental frequency of the voice and is a common cause of a deep, gravelly voice. In some cases, a naturally large laryngeal structure, unrelated to hormonal issues, places a woman at the lower end of the normal pitch distribution.
When to Seek Medical Evaluation and Voice Therapy
A voice change that is sudden, rapidly progressive, or persistent beyond a few weeks should prompt a medical consultation. If a lower voice is accompanied by other symptoms of hyperandrogenism, such as increased body hair (hirsutism) or menstrual irregularities, an evaluation by an endocrinologist is warranted to test hormone levels. Persistent hoarseness, pain while speaking, vocal fatigue, or throat clearing lasting more than two to three weeks should be evaluated by an otolaryngologist (ENT doctor).
The otolaryngologist, or a subspecialist called a laryngologist, can perform a thorough examination of the vocal folds using techniques like laryngoscopy or videostroboscopy. This visual assessment helps diagnose structural issues such as nodules, polyps, or signs of chronic irritation. If a behavioral cause is suspected, a Speech-Language Pathologist (SLP) specializing in voice therapy can provide management. Voice therapy involves vocal training to modify speaking habits, reduce strain, and establish a more efficient and comfortable pitch and projection.