Can Dogs Hear?

Complexity level:	8
Project cost ($):	200
Time required:	1 day to prepare, 1 day for the science project experiment
Material availability:	High frequency sound generators may be obtained from a physics lab or purchased. They are fairly inexpensive. The participation of many different breeds of dogs, of different ages, is required. Try asking friends and family if they have dogs that fit the p
Safety concerns:	Ensure that the dogs are handled at all times by a qualified dog trainer, to avoid being bitten/injury. It is possible that the dogs may become agitated by the high frequency sounds.

Hypothesis

Dogs become more deaf as they grow older.

Overview

Dog’s hearing

The hearing ability of a dog depends on its breed and age. Dogs normally can are able to hear sounds in the range of 40Hz to 60,000Hz. They will prick their ears towards the source of the sound in order to maximize reception of the sound. The dog’s ear has up to 19 muscles that helpo rotate and tilt the ears. The shape of a dog’s ears also allows sound to be heard more accurately.

Dogs are able to hear sounds that are of a higher frequency range than humans are able to detect. Just like humans, the hearing ability of a dog diminishes with its age. This is especially true for certain breeds of dogs such as German shepherds, Poodles and Terriers. The life expectancy of a dog depends on its breed and size. Large sized dogs typically live between 7 to 13 years while smaller dogs can live up to 16 years.

Ultrasonic whistles are normally used in the training of dogs. Our human ears are unable to hear these high pitched ultrasonic sounds but dogs are in fact, able to respond better to sounds at these levels.

Scientific Terms

Hearing ability, breed, muscles, life expectancy

Materials

The materials required for this science fair project:
- a young and an older German Shepherd
- a young and an older Labrador
- a young and an older Terrier
- a young and an older Golden Retriever
- a young and an older Beagle Shepherd
- a young and an older Poodle
(the young dogs were approximately 3 years of age, whilst the older dogs were approximately 8 years of age)
- a dog trainer
- 1 box of dog biscuits
- a high frequency sound generator. We used a Digital Function Waveform Generator which had a frequency response range of 1Hz to 10000 KHz.
- a quiet room

Procedure

1. For this science fair project, the independent variables were the frequency of the sound, the dog’s age and the breed of the dogs tested - German shepherd, Labrador, Terrier, Golden Retriever and a Poodle. The dependent variable is the highest frequency of sound heard by the dog. This is determined by observing the reaction or response of the dog. The constants (control variables) are the distance of the sound source from the dog and the volume of the sound.

2. The six breeds of dogs chosen for the science project were the German shepherd, Labrador, Terrier, Golden Retriever and Poodle. One dog approximately3 years of age and another dog approximately 8 years of age, of each breed were found for this science fair project.

3. A quite room was chosen and the high frequency sound generator was set up in the room. The frequencies chose for this experiment were 5kHz, 10kHz, 15kHz, 20kHz, 25kHz, 30kHz, 35kHz, 40kHz, 45kHz and 50kHz. (Human ears may not hear sounds beyond 20 kHz).

4. The dogs were led into the room one at a time. The generator set to produce a 5 kHz sound. The reaction of the dog was observed. If the dog barked, turned to look at the sound source, or its ear perked or twitched, we recorded that the dog had reacted to the sound. The dog was given a biscuit treat and 5 minutes rest. After that the 10 kHz sound was generated and the dog observed again. This process of testing was repeated until the highest audible sound frequency for the dog was determined. Our results were carefully recorded.

5. The process as repeated on the remaining 11 dogs and the results are recorded in the table given below.

Results

It was observed that the older (8 year-old) dogs had poorer hearing abilities compared to the 3 year -old dogs. This was especially apparent for the German shepherd and the Poodle.

Dog age	Dogs age and their highest audible hearing range (kHz)
German shepherd	Labrador	Terrier	Golden Retriever	Beagle	Poodle
3 years	40	35	40	40	35	40
8 years	15	25	20	20	20	15

The chart below represents the result of our science project experiment.

dog age and hearing ability experiment

Conclusion

The hypothesis that dogs grow more deaf as they grow older, has indeed been proven to be true.

A dog’s extremely sharp hearing and sense of smell makes it very suitable for hunting and to serve as a guard dogs. Their hearing enables them to detect the faintest of sounds. Police K-9 units deploy dogs, usually German Shepherds, to help solve crimes. Police dogs also help sniff out contraband, drugs and other dangerous substances.

Also consider

To improve the reliability of our results, we could have perhaps used a larger number of breeds or tested dogs of a wider age gap. We could consider repeating this science fair project by comparing the difference in hearing deterioration between small breed dogs and larger breeds.

Another possibility would be to compare the effect of age and hearing in other domesticated animals like cats and birds, and perhaps even fish!

References

Hearing range - http://en.wikipedia.org/wiki/Hearing_range

Aging in dogs - http://en.wikipedia.org/wiki/Aging_in_dogs

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