Temporary threshold shift from a toy cap gun

Systematic Assessment of Noise Amplitude Generated by Toys Intended for Young Children

Objective

To systematically evaluate the noise generated by toys targeted for children and to compare the results over the course of 4 consecutive holiday shopping seasons.

Study Design

Experimental study.

Setting

Academic medical center.

Subjects and Methods

During 2008-2011, more than 200 toys marketed for children older than 6 months were screened for loudness. The toys with sound output of more than 80 dBA at speaker level were retested in a soundproof audiometry booth. The generated sound amplitude of each toy was measured at speaker level and at 30 cm away from the speaker.

Results

Ninety different toys were analyzed. The mean (SD) noise amplitude was 100 (8) dBA (range, 80-121 dBA) at the speaker level and 80 (11) dBA (range, 60-109 dBA) at 30 cm away from the speaker. Eighty-eight (98%) had more than an 85-dBA noise amplitude at speaker level, whereas 19 (26%) had more than an 85-dBA noise amplitude at a 30-cm distance. Only the mean noise amplitude at 30 cm significantly declined during the studied period ( P < .001). There was no significant difference in mean noise amplitude of different toys specified for different age groups.

Conclusion

Our findings demonstrate the persistence of extremely loud toys marketed for very young children. Acoustic trauma from toys remains a potential risk factor for noise-induced hearing loss in this age group, warranting promotion of public awareness and regulatory considerations for manufacture and marketing of toys.

Temporary shift in masked hearing thresholds of bottlenose dolphins, Tursiops truncatus, and white whales, Delphinapterus leucas, after exposure to intense tones

A behavioral response paradigm was used to measure masked underwater hearing thresholds in five bottlenose dolphins and two white whales before and immediately after exposure to intense 1-s tones at 0.4, 3, 10, 20, and 75 kHz. The resulting levels of fatiguing stimuli necessary to induce 6 dB or larger masked temporary threshold shifts (MTTSs) were generally between 192 and 201 dB re: 1 microPa. The exceptions occurred at 75 kHz, where one dolphin exhibited an MTTS after exposure at 182 dB re: 1 microPa and the other dolphin did not show any shift after exposure to maximum levels of 193 dB re: 1 microPa, and at 0.4 kHz, where no subjects exhibited shifts at levels up to 193 dB re: 1 microPa. The shifts occurred most often at frequencies above the fatiguing stimulus. Dolphins began to exhibit altered behavior at levels of 178-193 dB re: 1 microPa and above; white whales displayed altered behavior at 180-196 dB re: 1 microPa and above. At the conclusion of the study all thresholds were at baseline values. These data confirm that cetaceans are susceptible to temporary threshold shifts (TTS) and that small levels of TTS may be fully recovered.

Noise level analysis of commercially available toys

There have been several isolated reports of hearing loss due to noise levels from toys. Guidelines for noise production by toys is regulated by the Voluntary Product Standards PS 72-76: Toy Safety Act of 1969. To determine the current risk of noise induced hearing loss from toys currently on the market, 25 toys were purchased at a national toy store chain and sound levels were measured at distances approximating ear level (2.5 cm) and a child's arm length (25 cm) from the surface of the toy. Testing revealed peak sound levels ranging from 81 to 126 dBA at 2.5 cm and 80 to 115 dBA at 25 cm from the surface of the toy.

Inner ear damage from toy cap pistols and fire-crackers

Groups of guinea pigs comprising 7 animals in each group were exposed to 10, 50 or 100 exposures to fire-crackers or 10, 50 or 100 exposures to toy cap pistol shots. An additional group of 7 animals comprised the control material. The exposures were performed with 15-s intervals at 0.25 m distance for the toy cap pistol shots and at 0.8 m for the fire-crackers. The peak sound level at the ear was 155 dBC for both impulsive sounds. After a 3-week survival period the animals were anesthetized and decapitated. The cochleas were examined histologically in surface preparations and read double-blind. One animal in each group exposed to 10 fire-crackers and 10 toy cap pistol shots showed sensory cell loss. With 50 or 100 toy cap pistol shots or fire-cracker exposures, 24 out of 28 animals showed pronounced sensory cell loss. The present results clearly indicate the risk for noise-induced hearing loss in children playing with toy cap guns and fire-crackers.

Early noise-induced hearing loss in teenage boys

A hearing examination of 538 teenage boys in vocational school classes--implying future on-the-job noise exposure--showed a hearing loss (greater than 20 dB HL at any frequency) in 15% of the cases. Few correlations could be demonstrated between hearing loss and specific leisure time activities. There was, however, a correlation between high frequency hearing loss in the left ear and hereditary hearing loss. The most affected frequency was 6 kHz, suggesting a noise etiology--a suggestion emphasized by the noisy hobbies of these teenagers. It cannot be excluded that a hereditary deficiency could either manifest itself as a localized dip at 6 kHz or reveal itself as an increased vulnerability to noise, identified at young age as a high frequency dip at 6 kHz.