Cochlear implant has benefited thousands of patients with profound sensorineural hearing loss by providing satisfactory speech perception. Due to limited pitch information encoded in current speech processing strategies, tone perception and music perception are still challenging to users of cochlear implants. For patients who speak tone languages, such as Mandarin Chinese, tone perception is critical because tones convey lexical meaning at monosyllable levels. Tone perception and tone production in prelingually-deafened children have been studied for many years but not in real-world situations. The purpose of the proposed study is to investigate tone development in the rapidly increasing number of Mandarin-speaking children with cochlear implants in real-world situations. Specific Aim 1 of the proposed study addresses lexical tone perception in noise conditions in both Mandarin-speaking normal-hearing children and children with cochlear implants. One-hundred sixty normal-hearing, native Mandarin-speaking children and 100 prelingually- deafened children with cochlear implants between 3 and 18 years of age will be recruited to participating in tone perception experiment conducted in various noise types (i.e., steady-state noise, amplitude-modulated noised, and multi-talker speech babble noise) at various signal-to-noise ratios (i.e., from -6 to +12 dB). Another group of 20 normal-hearing adults will also be recruited as controls. In Specific Aim 2, the same groups of children subjects (i.e., normal-hearing and those with cochlear implants) as well as adult subjects will be recorded producing a listed of disyllable Chinese words and spontaneous production of sentences. The recorded speech materials will be subject to acoustic and neural-network analysis that we developed previously. The acoustic analysis will focus on the fundamental frequencies (F0) of the speech samples. The neural network analysis will be used to provide an objective measure of tone production accuracy of the children with cochlear implants based on the tone patterns of the adults and age-matched, typical developing children. Special attention will be paid in coarticulation of the tone patterns between syllables. Multiple regression analyses will be performed to identify any associations of age at implantation and duration of implant use with the tone perception in noise and tone production accuracy beyond monosyllable levels. Therefore, the proposed study represents tone development in real-world situations in children with normal hearing and cochlear implants. Although the proposed study is primarily concerned with lexical tone development, it has important implications for speakers of non-tonal languages because pitch information is used in auditory stream segregation as well as in music perception. Therefore, the proposed study could help improve quality of life for many cochlear implant users.