151st ASA Meeting, Providence, RI

Quiet, I'm Trying to Learn language!
The Effect of Background Noise on Infants

Rochelle Newman- rnewman@hesp.umd.edu
Dept. of Hearing & Speech Sciences
University of Maryland
College Park, MD 20742

Popular version of paper 3aSC22
Presented Wednesday morning, June 7, 2006
151st ASA Meeting, Providence, RI

Cars screech across the TV screen; siblings bicker in another room; the blender whirrs in the kitchen; and somehow, in the midst of all the noise, an infant sifts the sound of her own name out of the tumult and responds.

This environment, typical of modern households, could not be more different than the quiet laboratory settings in which most research on how infants learn language has taken place. The present research examines how the type of background noise influences infants' ability to understand speech.

The study examined how long a 4.5-month-old child spent listening when a female voice said either the baby's name or another infant's name in the presence of background noise. Prior research in quiet labs has shown that at 4.5 months, babies will listen longer to their own name than to someone elese's (Mandel, Jusczyk & Pisoni, 1995). We examined if this would hold true in the midst of different types of noise.

In particular, we compared a situation akin to a day care (with multiple people talking in the background) to something more common in a home setting (with only a single person talking in the background).




Testing

Infants sat on their caregiver's lap in a three-sided booth. A light on one of the side panels attracted the infants' attention; once the infant was looking in that direction, the woman's voice began calling a name. On some trials, the name was that of the infant being tested; on other trials, it was the name of a different child. The woman continued to repeat the name until the baby turned his or her head away, and we measured the amount of time each infant spent listening to the different names. In all three cases, the target woman's voice was 10 decibels louder than the sounds of the other people talking; this is roughly equivalent to the noise level you might experience while having a one-on-one conversation at a reasonably quiet restaurant (one filled with other patrons, but in which people are speaking softly).

Results

Infants heard the names in the presence of three different types of noise: a mix of multiple background talkers, a single background talker, and a single background talker reversed in time (this has the acoustic properties of a single talker, but doesn't sound like real speech) ; examples of these sounds are presented below.

When the noise consisted of multiple people speaking at the same time, infants listened longer to their names than to the names of other children. However, they only did so when the target speech was at least 10 dB more intense than the background - a less noisy situation than that typically found in day care settings (see, for example, http://www.acoustics.org/pressroom/httpdocs/139th/golden.htm).

Sample 1
Sample 2

But even at this high amplitude level, infants appeared able to recognize their own name when the background noise blended to a murmur, but clearly found the task far more difficult when the background signal was a single voice. This is particularly surprising, because adult listeners show the exact opposite pattern.

Sample 3
Sample 4

Summary:

The present results suggest that listening in noise is a more difficult task for infants when the "noise" consists of a single talker than multiple talkers. Moreover, this was the case even when the talker was much louder than the background noise.

These findings suggest that children may experience difficulties listening in many of the settings where they commonly find themselves. Often, in the home, background noise takes the form of other voices, and there generally may not be so many other voices that they blend into background babble. A parent may be talking to her infant while someone is talking on the phone, or while the other parent is speaking to a sibling. These situations are much more akin to the single-voice condition presented here, and the present results suggest that infants may have a very difficult time understanding what is said to them in these situations. Moreover, the fact that adults show just the opposite pattern suggests the possibility that parents may frequently underestimate the extent of the noise problem facing their child.

These results imply that noise could interfere with children's language development, suggesting the need for greater parental awareness of the noise in their infants' environments.

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