The symptoms you describe may be consistent with autism; however they may also be caused by other conditions. The first thing is to rule out a possible undiagnosed hearing loss. This may not be possible with a standard-head-phones-on hearing test. An auditory brainstem response (ABR) test may be necessary to determine hearing acuity.

Another area that should be evaluated is the possibility of sensory integration (SI) difficulties which may cause symptoms of autism. In fact lots of children with autism may have SI problems, but not all children with SI problems have autism. In general if a child is not using 50 words by the age of 24 months, their language is considered to be delayed; however, some children are simply late talkers and will eventually catch up.

It can be challenging to differentiate those children who have SI difficulties and are late talkers, from those children who have autism. However, it is very important that this differential diagnosis be made, so that the child can receive appropriate intervention to be able to achieve their greatest potential. There needs to be team approach to evaluation and treatment. Some of the professionals involved may include the pediatrician, a child psychologist, an occupational therapist and a speech-language pathologist.

From the Mayo Clinic page on the symptoms of Autism:
"Children with autism generally have problems in three crucial areas of development — social interaction, language and behavior. But because autism symptoms vary greatly, two children with the same diagnosis may act quite differently and have strikingly different skills. In most cases, though, severe autism is marked by a complete inability to communicate or interact with other people.

Some children show signs of autism in early infancy. Other children may develop normally for the first few months or years of life but then suddenly become withdrawn, become aggressive or lose language skills they've already acquired. Though each child with autism is likely to have a unique pattern of behavior, these are some common autism symptoms:

Social skills

Fails to respond to his or her name
Has poor eye contact
Appears not to hear you at times
Resists cuddling and holding
Appears unaware of others' feelings
Seems to prefer playing alone — retreats into his or her "own world"
Language

Starts talking later than age 2, and has other developmental delays by 30 months
Loses previously acquired ability to say words or sentences
Doesn't make eye contact when making requests
Speaks with an abnormal tone or rhythm — may use a singsong voice or robot-like speech
Can't start a conversation or keep one going
May repeat words or phrases verbatim, but doesn't understand how to use them
Behavior

Performs repetitive movements, such as rocking, spinning or hand-flapping
Develops specific routines or rituals
Becomes disturbed at the slightest change in routines or rituals
Moves constantly
May be fascinated by parts of an object, such as the spinning wheels of a toy car
May be unusually sensitive to light, sound and touch and yet oblivious to pain
Young children with autism also have a hard time sharing experiences with others. When read to, for example, they're unlikely to point at pictures in the book. This early-developing social skill is crucial to later language and social development.

As they mature, some children with autism become more engaged with others and show less marked disturbances in behavior. Some, usually those with the least severe problems, eventually may lead normal or near-normal lives. Others, however, continue to have difficulty with language or social skills, and the adolescent years can mean a worsening of behavioral problems.

Most children with autism are slow to gain new knowledge or skills, and some have signs of lower than normal intelligence. Other children with autism have normal to high intelligence. These children learn quickly yet have trouble communicating, applying what they know in everyday life and adjusting in social situations. A small number of children with autism are "autistic savants" and have exceptional skills in a specific area, such as art, math or music.

When to see a doctor
Babies develop at their own pace, and many don't follow exact timelines found in some parenting books. But children with autism usually show some signs of delayed development by 18 months. If you suspect that your child may have autism, discuss your concerns with your doctor. The earlier treatment begins, the more effective it will be.

Your doctor may recommend further developmental tests if your child:

Doesn't babble or coo by 12 months
Doesn't gesture — such as point or wave — by 12 months
Doesn't say single words by 16 months
Doesn't say two-word phrases by 24 months
Loses previously acquired language or social skills at any age"