Inclusion Criteria:  Subject has read and voluntarily signed the Informed Consent Form (ICF) after all questions have been answered and prior to any study-mandated procedure. Adult aged 18-65 years inclusive at Screening. Documented medical history consistent with acquired, adult onset, sensorineural hearing loss associated with noise-induced SNHL (NIHL) or idiopathic sudden SNHL (SSNHL) (documented audiogram at least 6 months prior to screening required). A pure tone average at the Screening Visit of 35-85 dB at 500Hz, 1000Hz, 2000Hz, and 4000Hz in the ear to be injected. Ability to communicate well with the Investigator and is willing to comply with and complete all the study procedures. Female subjects must be of non-childbearing potential or will need to utilize two methods of highly effective contraception during the study participation (e.g. hormonal contraception and condom or an intrauterine device and condom) or remain abstinent. Male subjects should use condoms with spermicide during the course of the study or remain abstinent. Subjects should not donate sperm or ova during the study period. Have met additional masked criteria as determined by the Electronic Data Capture system.  Exclusion Criteria:  Subject has previously been randomized in a FX-322 clinical trial. Perforation of tympanic membrane or other tympanic membrane disorders that would interfere with the delivery and safety assessment of an intratympanic medication or reasonably be suspected to affect tympanic membrane healing after injection in study ear. This includes a current tympanostomy tube. Any conductive hearing loss of greater than 15 dB at a single frequency or greater than 10dB at two or more contiguous octave frequencies in the study ear at the Screening visit. Active chronic middle ear disease or a history of major middle ear surgery, as an adult, in the ear to be injected. Subject has had an intratympanic injection in either ear within 3 months of the screening visit. Evidence of or previous diagnosis of auditory neuropathy, traumatic brain injury, "central" hearing loss, or genetic hearing loss. History of chronic, recurrent clinically significant vestibular symptoms. History of bilateral sudden sensorineural hearing loss or recurrent sudden sensorineural hearing loss. History of clinically significant systemic autoimmune disease (e.g. rheumatoid arthritis, Sjogren's syndrome, multiple sclerosis, psoriasis). History of head or neck radiation, treatment, or exposure to platinum based chemotherapy drugs or aminoglycosides. Exposure to another investigational drug within 28 days prior to screening visit. Evidence of any active or chronic disease or condition that could interfere with, or for which the treatment of might interfere with, the conduct of the study, or that would pose an unacceptable risk to the subject in the opinion of the investigator following a detailed medical history, physical examination, and vital signs (systolic and diastolic blood pressure, pulse rate, body temperature). Positive urine pregnancy test or breast-feeding. Any known factor, condition, or disease that, in the view of the Investigator, might interfere with treatment compliance, study conduct or interpretation of the results.