自由场法测量声功率.docx
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自由场法测量声功率
实验四自由场法测量声功率
一、实验目的
掌握半消声室精密法测声功率的原理和方法。
二、实验要求
1.在消声室采用半球面作为测量表面。
2.每个测点测量1次。
三、实验环境
1．半消声室
2．噪声源（以320W大宇6060T手电钻为例）
3．HS6288B声级计（2型）
4．1／2吋传声器延长电缆
5．传声器支架
四、实验内容、步骤
1.实验内容：
测量电钻空载时的声功率
2.实验原理：
噪声源的辐射特性通常用指向特性和辐射功率描述。
声功率的单位为瓦，如用声功率级表示，则
式中
为声源辐射功率，
为声功率级（dB）；基准声功率为10－12W。
3.指向性声源的声功率测量
将声源放在自由场中，测量出声源周围固定距离处假想球面上许多点的声压级，球的半径应该使测量点位于远场。
测量点数目不能太少，测得数值之间的最大变化不得超过6dB左右，否则必须在更多的点上进行测量。
确定声源的声功率时，将假想球面分成与测点数目相同的面积，传声器测点占有的测试半球的面积相等，用下式求出表面平均声压级：
式中
是表面平均声压级；
是第i个测点的声压级，N是测点数目。
这时自由场中噪声的声功率为：
式中
是测试球面上表面平均声压级,
。
下面给出以声源为原点测点的直角坐标（x,y,z），z轴选择垂直于水平面向上的方向。
表4.1测点直角坐标分布如下:
测点号
x/r
y/r
z/r
1
2
3
4
5
6
7
8
9
10
-0.99
0.50
0.50
–0.45
–0.45
0.89
0.33
–0.66
0.33
0
0
-0.86
0.86
0.77
–0.77
0
0.57
0
-0.57
0
0.15
0.15
0.15
0.45
0.45
0.45
0.75
0.75
0.75
0
4.实验步骤
将HS自由场传声器装加在HS6288B声级计的延长电缆上并进行校准，在消声室地面中央处画圆确定测量表面的位置，将电钻置于圆心，将传声器夹在支架上，调整支架延伸杆的长度及角度，按图1确定测点位置依次测量各点声压级，按上式计算被测电钻的声功率级。
五、实验结果
1.每个测点的原始记录数据：
半球半径r=0.8m
测点1的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
4.26850e+001
2
8.0000000000e+001
3.91176e+001
3
1.0000000000e+002
4.49067e+001
4
1.2500000000e+002
4.87235e+001
5
1.6000000000e+002
5.65264e+001
6
2.0000000000e+002
6.03713e+001
7
2.5000000000e+002
5.54823e+001
8
3.1500000000e+002
6.13301e+001
9
4.0000000000e+002
6.27448e+001
10
5.0000000000e+002
5.83394e+001
11
6.3000000000e+002
5.23349e+001
12
8.0000000000e+002
5.74655e+001
13
1.0000000000e+003
6.23429e+001
14
1.2500000000e+003
5.09674e+001
15
1.6000000000e+003
5.11164e+001
16
2.0000000000e+003
5.50970e+001
17
2.5000000000e+003
5.07698e+001
18
3.1500000000e+003
4.81345e+001
19
4.0000000000e+003
5.05024e+001
20
5.0000000000e+003
4.33621e+001
21
6.3000000000e+003
3.89355e+001
22
8.0000000000e+003
3.92586e+001
23
1.0000000000e+004
3.95506e+001
24
1.2500000000e+004
3.59386e+001
测点2的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.85848e+001
2
8.0000000000e+001
3.07662e+001
3
1.0000000000e+002
3.49995e+001
4
1.2500000000e+002
3.67705e+001
5
1.6000000000e+002
4.44302e+001
6
2.0000000000e+002
4.86575e+001
7
2.5000000000e+002
4.85217e+001
8
3.1500000000e+002
6.02939e+001
9
4.0000000000e+002
5.87627e+001
10
5.0000000000e+002
6.10334e+001
11
6.3000000000e+002
6.16746e+001
12
8.0000000000e+002
5.91776e+001
13
1.0000000000e+003
6.38973e+001
14
1.2500000000e+003
6.22307e+001
15
1.6000000000e+003
6.61915e+001
16
2.0000000000e+003
6.68039e+001
17
2.5000000000e+003
7.65683e+001
18
3.1500000000e+003
7.62447e+001
19
4.0000000000e+003
7.22631e+001
20
5.0000000000e+003
6.83699e+001
21
6.3000000000e+003
6.55720e+001
22
8.0000000000e+003
6.60565e+001
23
1.0000000000e+004
6.48718e+001
24
1.2500000000e+004
6.30553e+001
测点3的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.86541e+001
2
8.0000000000e+001
3.17247e+001
3
1.0000000000e+002
4.22254e+001
4
1.2500000000e+002
3.91409e+001
5
1.6000000000e+002
4.55951e+001
6
2.0000000000e+002
4.82254e+001
7
2.5000000000e+002
4.99764e+001
8
3.1500000000e+002
5.81686e+001
9
4.0000000000e+002
5.70080e+001
10
5.0000000000e+002
5.97292e+001
11
6.3000000000e+002
6.09798e+001
12
8.0000000000e+002
6.41925e+001
13
1.0000000000e+003
6.98105e+001
14
1.2500000000e+003
7.22627e+001
15
1.6000000000e+003
7.24525e+001
16
2.0000000000e+003
6.95435e+001
17
2.5000000000e+003
7.46119e+001
18
3.1500000000e+003
6.90675e+001
19
4.0000000000e+003
7.62461e+001
20
5.0000000000e+003
7.48683e+001
21
6.3000000000e+003
6.74903e+001
22
8.0000000000e+003
6.70415e+001
23
1.0000000000e+004
6.67820e+001
24
1.2500000000e+004
6.49849e+001
测点4的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.41419e+001
2
8.0000000000e+001
2.85947e+001
3
1.0000000000e+002
4.05011e+001
4
1.2500000000e+002
3.30512e+001
5
1.6000000000e+002
3.69295e+001
6
2.0000000000e+002
4.30127e+001
7
2.5000000000e+002
4.66979e+001
8
3.1500000000e+002
5.76067e+001
9
4.0000000000e+002
5.59737e+001
10
5.0000000000e+002
6.05978e+001
11
6.3000000000e+002
6.31712e+001
12
8.0000000000e+002
6.71766e+001
13
1.0000000000e+003
7.04580e+001
14
1.2500000000e+003
7.16968e+001
15
1.6000000000e+003
6.91766e+001
16
2.0000000000e+003
7.38660e+001
17
2.5000000000e+003
7.05139e+001
18
3.1500000000e+003
7.12660e+001
19
4.0000000000e+003
7.52949e+001
20
5.0000000000e+003
6.99514e+001
21
6.3000000000e+003
6.90324e+001
22
8.0000000000e+003
6.77035e+001
23
1.0000000000e+004
6.56655e+001
24
1.2500000000e+004
6.44730e+001
测点5的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.45747e+001
2
8.0000000000e+001
2.62489e+001
3
1.0000000000e+002
3.17236e+001
4
1.2500000000e+002
3.83195e+001
5
1.6000000000e+002
4.47805e+001
6
2.0000000000e+002
4.71485e+001
7
2.5000000000e+002
4.87424e+001
8
3.1500000000e+002
5.98320e+001
9
4.0000000000e+002
5.77249e+001
10
5.0000000000e+002
6.00334e+001
11
6.3000000000e+002
6.22407e+001
12
8.0000000000e+002
6.54265e+001
13
1.0000000000e+003
6.85357e+001
14
1.2500000000e+003
6.80967e+001
15
1.6000000000e+003
6.94998e+001
16
2.0000000000e+003
6.59071e+001
17
2.5000000000e+003
7.19332e+001
18
3.1500000000e+003
7.28463e+001
19
4.0000000000e+003
7.15122e+001
20
5.0000000000e+003
7.04118e+001
21
6.3000000000e+003
6.61315e+001
22
8.0000000000e+003
6.50594e+001
23
1.0000000000e+004
6.70321e+001
24
1.2500000000e+004
6.18396e+001
测点6的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.80322e+001
2
8.0000000000e+001
3.08437e+001
3
1.0000000000e+002
3.63733e+001
4
1.2500000000e+002
3.58923e+001
5
1.6000000000e+002
4.20785e+001
6
2.0000000000e+002
4.03788e+001
7
2.5000000000e+002
4.42155e+001
8
3.1500000000e+002
4.93321e+001
9
4.0000000000e+002
5.31587e+001
10
5.0000000000e+002
5.65769e+001
11
6.3000000000e+002
5.98299e+001
12
8.0000000000e+002
6.58934e+001
13
1.0000000000e+003
7.10451e+001
14
1.2500000000e+003
7.03120e+001
15
1.6000000000e+003
6.86253e+001
16
2.0000000000e+003
7.08321e+001
17
2.5000000000e+003
6.92552e+001
18
3.1500000000e+003
6.84775e+001
19
4.0000000000e+003
7.39125e+001
20
5.0000000000e+003
7.00372e+001
21
6.3000000000e+003
6.67916e+001
22
8.0000000000e+003
6.54144e+001
23
1.0000000000e+004
6.61451e+001
24
1.2500000000e+004
6.39371e+001
测点7的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
5.87263e+001
2
8.0000000000e+001
5.72207e+001
3
1.0000000000e+002
5.17067e+001
4
1.2500000000e+002
4.85478e+001
5
1.6000000000e+002
4.67473e+001
6
2.0000000000e+002
4.57892e+001
7
2.5000000000e+002
4.72410e+001
8
3.1500000000e+002
5.55667e+001
9
4.0000000000e+002
5.69116e+001
10
5.0000000000e+002
5.87219e+001
11
6.3000000000e+002
6.28192e+001
12
8.0000000000e+002
6.96265e+001
13
1.0000000000e+003
7.27475e+001
14
1.2500000000e+003
7.01544e+001
15
1.6000000000e+003
6.93641e+001
16
2.0000000000e+003
7.13205e+001
17
2.5000000000e+003
7.50484e+001
18
3.1500000000e+003
7.33248e+001
19
4.0000000000e+003
7.40256e+001
20
5.0000000000e+003
6.90320e+001
21
6.3000000000e+003
6.61139e+001
22
8.0000000000e+003
6.72157e+001
23
1.0000000000e+004
6.51052e+001
24
1.2500000000e+004
6.15588e+001
测点8的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.79751e+001
2
8.0000000000e+001
2.91717e+001
3
1.0000000000e+002
3.74784e+001
4
1.2500000000e+002
3.70162e+001
5
1.6000000000e+002
4.25198e+001
6
2.0000000000e+002
4.26275e+001
7
2.5000000000e+002
4.58913e+001
8
3.1500000000e+002
5.66895e+001
9
4.0000000000e+002
5.57578e+001
10
5.0000000000e+002
5.86699e+001
11
6.3000000000e+002
6.35316e+001
12
8.0000000000e+002
7.03141e+001
13
1.0000000000e+003
7.40493e+001
14
1.2500000000e+003
6.95273e+001
15
1.6000000000e+003
6.67842e+001
16
2.0000000000e+003
7.21716e+001
17
2.5000000000e+003
7.64255e+001
18
3.1500000000e+003
7.49823e+001
19
4.0000000000e+003
7.39499e+001
20
5.0000000000e+003
7.01009e+001
21
6.3000000000e+003
7.08282e+001
22
8.0000000000e+003
6.72810e+001
23
1.0000000000e+004
6.49728e+001
24
1.2500000000e+004
6.54819e+001
测点9的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.66892e+001
2
8.0000000000e+001
2.83850e+001
3
1.0000000000e+002
3.63599e+001
4
1.2500000000e+002
3.64220e+001
5
1.6000000000e+002
4.21315e+001
6
2.0000000000e+002
4.34957e+001
7
2.5000000000e+002
4.57244e+001
8
3.1500000000e+002
4.96399e+001
9
4.0000000000e+002
5.32388e+001
10
5.0000000000e+002
5.77944e+001
11
6.3000000000e+002
6.40408e+001
12
8.0000000000e+002
6.64229e+001
13
1.0000000000e+003
7.01934e+001
14
1.2500000000e+003
6.94370e+001
15
1.6000000000e+003
6.63248e+001
16
2.0000000000e+003
7.21457e+001
17
2.5000000000e+003
7.47658e+001
18
3.1500000000e+003
7.42276e+001
19
4.0000000000e+003
7.61133e+001
20
5.0000000000e+003
7.03365e+001
21
6.3000000000e+003
6.65539e+001
22
8.0000000000e+003
6.75153e+001
23
1.0000000000e+004
6.48808e+001
24
1.2500000000e+004
6.45882e+001
测点10的记录数据
序号
频率（Hz）
声压级（dB）
1
6.3000000000e+001
2.79003e+001
2
8.0000000000e+001
2.71257e+001
3
1.0000000000e+002
3.56100e+001
4
1.2500000000e+002
3.31189e+001
5
1.6000000000e+002
3.83103e+001
6
2.0000000000e+002
4.24349e+001
7
2.5000000000e+002
4.67852e+001
8
3.1500000000e+002
5.70304e+001
9
4.0000000000e+002
5.96226e+001
10
5.0000000000e+002
6.35944e+001
11
6.3000000000e+002
6.63078e+001
12
8.0000000000e+002
6.95178e+001
13
1.0000000000e+003
6.95546e+001
14
1.2500000000e+003
6.91461e+001
15
1.6000000000e+003
6.87565e+001
16
2.0000000000e+003
7.12519e+001
17
2.5000000000e+003
7.27371e+001
18
3.1500000000e+003
6.92435e+001
19
4.0000000000e+003
7.12147e+0
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